Tag Archives: Chemical Safety

Risk and Regulations: An Epistle to the Bohemians, Redux.

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Attached is an updated reprint of an essay I posted 10/28/07. Since then I have shifted into EPA regulatory compliance within the chemical industry. My views have changed a little, it turns out.

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“We live in an age of miracle and wonder” is the refrain from Paul Simon’s album Graceland. All around us and through us are engineered materials devised for their specific physical and chemical properties. Time-released magic bullet drugs that inhibit specific enzymes. Flavors & fragrances, colorants, rheology modifiers, UV absorbers, emollients, preservatives, food irradiation and manufactured food additives are engineered and marketed to satisfy our lizard brain’s willingness to shell out cash-for-fun and stimulate our limbic system’s emotive triggers. 

It is hard to avoid contact with manufactured goods that aren’t affected by chemistry. A century and a half of tinkering with substances at the molecular scale has given us the ability to optimize the composition and performance of products that make our lives easier and safer.  Microprocessors and Lycra, Hastelloy and Lipitor- the chemical industry has evolved to produce the raw materials and finished goods needed for the performance we have come to expect.

Industry has a Spotty Record of Safety

Along with the considerable list of positive contributions, history provides a detailed record of the problems associated with the exuberant but uncritical acceptance of the flood of manufactured goods.  From radium poisoning of watch dial painters to chromium VI to asbestos, there is a long list of accidents, ignorance, negligence and environmental insult. The trail blazing of our chemical industry leaves behind it a chronicle of tragedy as well as benefits.

The result of the checkered past of industry is a growing (some would say “metastasizing”) and intertwined web of state, federal, and international regulatory oversight and requirements. And with it- arguably as a result of it- has come greater institutional risk aversion. 

Risk Aversion

In a general way, risk aversion is a type of survival trait and is likely hardwired into our ape brains. It is hard to blame people for being wary or fearful of risks, especially those they do not understand. Over time risk aversion is useful survival trait. But on the other hand, risk aversion is also a type of inertia. Or, it can be a fulcrum from which policy and imaginary justifications are leveraged.  The fear of risk may be firmly grounded on experience or it might be imagined or a mixture of the two. The hard part of risk management is identifying real hazards and the probability and magnitude of a bad outcome for managing safety day-to-day. Basically, the hard part is the whole part.

Risk = Probability x Severity of a negative outcome.

Corporate officers have a fiduciary responsibility to the stockholders. They’re purpose is to maximize profits without undue risk to the organization. Most respond to the regulatory environment by perhaps heaving a sigh and relenting to the requirements. Regulatory compliance can have costs associated with it like animal testing of chemical products and intermediates, or engineering upgrades and these costs need to be built into annual budgetary calculations.

How Granular Does Safety Have to Be?

Can safety practices be excessive? I would say that if some specific activity is based on imaginary risks, risks identified by the untrained or massively overestimated risks, the cold eyes of an industry consultant may be needed. Who knows, you may have actually underestimated a risk.

Safety has a large psychological component to it. How do you compel people to behave consistently in a way that keeps everyone safe? Not just immediately, but in the twentieth or five hundredth time they perform a task with associated hazards? Complacency is a normal human weakness where a misstep can lead to casualties.

The amount and type of safety measures in chemical processing required greatly depends on the chemical substance. Some company’s batch records give very detailed instructions to maintain constant safety. Others are less so on the assumption that the operations staff know what they are doing. Too much detail can lead to operator impatience and freelancing.

It is possible for organizations to be dominated by confident voices that are quite risk averse but not very knowledgeable about the technology. Leaders will state that “safety-first is our policy”.  A paper storm of SOPs will issue, dragging out the most elementary actions into numerous steps and check boxes. There is great merit to SOPs, but enlightened and proactive interpersonal management of hazardous operations is just as important. Management by walking around works.

Organizations can find themselves spiraling into micromanagement of even the smallest details for fear that the regulatory and liability hammer could fall at any moment. Indeed, if one studies many regulations in detail, it is easy to fall into habit of overreacting. Risk aversion isn’t just a personality issue, it is statutory under numerous regulatory umbrellas.

Being a baby boomer, the chemical safety practices I have been exposed to and have practiced is rather out of date. My education occurred during a time when running chemical reactions on an unventilated bench top was normal. We used Tirrill burners to flame dry our glassware on the sophomore organic lab benchtop and set the hot glass on a Transite square, an asbestos product from Johns Manville. I still would have no problem using Transite. In fact, I have done many things since summer of 1980 that would be frowned upon today. My grad school and post doc time went way into the weeds on using hazardous materials with minimal oversight.

You learn how to safely handle chemicals by safely handling chemicals. In the course of using a chemical, you might conclude that the known hazard of the substance appears to be exaggerated, so over time and repetition you let your safety practices loosen up a bit. Then one day, you cross some unseen line and an energetic event happens. While what you did leading to this outcome might be categorized as carelessness, as they drag you out of the lab by your one remaining arm, your ears ringing, a metallic taste in your mouth, and partially covered by your torn and smoldering lab coat, you recognize that you actually learned something from that experience. You now have a better appreciation for the safe operating range for that chemical. You’ve gotten one quantum unit of expertise. This is one way to gain expertise, albeit a painful one. Perhaps it will be useful once you start your next career. I have had many close calls and each one taught me something. Perversely, not having close calls with chemicals- some would call it luck -actually deprives one of practical and useful experience.

Today I am a senior chemist involved in chemical safety in industry. Until recently, I was involved in finding the thermal safety boundaries of chemical reactions through calorimetry. But with the past experience that I have, I know a bit more about the boundary conditions of handling chemicals than the younger chemists may get to acquire. In order to know how to work with hazardous chemicals you must have worked previously with hazardous chemicals and perhaps seen for yourself what can happen with sloppy technique.

This is nothing reckless like poking alligators with a stick in Florida or free climbing El Capitan. I mean things like seeing what actually happens when you pour concentrated H2SO4 into water fast enough right up to the boiling point taking care not to have a splash. Maybe you can see the heat of dilution boiling the water at the H2SO4/water interface.

The Regulatory Environment

Statutory risk aversion is the domain of the state. The name “Nanny State” is a sarcastic descriptor referring to a perceived excess of regulated requirements and conditions in our lives as well as the set of penalties.  Though perhaps well intended, the Nanny State seeks to zero out risk. Even if a situation arises for which there is no explicit regulation, OSHA has the General Duty Clause where employers are required to provide:

“employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees…”

This provision exists to address any gaps in OSHA regulations that may not account for unforeseen circumstances. The plethora of regulations is partly due to the vast array of situations in which industrial employees might be injured or killed. Additionally, lawyers have identified and exploited loopholes in the regulations, which are subsequently closed by regulatory agencies. Ambiguities are often resolved through statutory amendments or the application of established case law.

EPA TSCA has the job of generating and enforcing regulations regarding the manufacture and use of a range of industrial chemicals in a limited sector of manufacturing. The central doctrine is from:

As required under section 6(b)(4) of the Toxic Substances Control Act (TSCA), EPA is issuing a rule that establishes a process for conducting risk evaluations to determine whether a chemical substance presents an unreasonable risk of injury to health or the environment, without consideration of costs or other non-risk factors, including an unreasonable risk to a potentially exposed or susceptible subpopulation, under the conditions of use. [Emphasis mine]

TSCA does not include Food, Drugs, Petroleum, Pesticides and a few other areas.

The key words above are unreasonable risk. With every New Chemical Substance filing sent to the TSCA folks at EPA, an assessment must be made by various subgroups for unreasonable risk by the human health group, the engineering group and the environmental group. Thresholds for “unreasonable” have been quantified in order to exclude subjectivity. EPA has many computer models of exposure thresholds, migration in the soil and toxicity to many creatures including humans.

The regulatory environment can make the production of a new chemical substance more expensive or even unfeasible. Nobody advocates the idea that we should be free to pollute and risk the lives of workers and communities.  But even for the most skillful and well-intended, there are many regulatory landmines to dodge: air, water, and waste permits; local zoning; OSHA; EPA (TSCA); fire codes; insurance inspections; MSDS’s in multiple languages; ITAR; and DEA. All have reporting requirements, statutes, and paper trails to maintain.

Pragmatics

There are two kinds of disaster that can bring down a chemical plant. One is obviously a fire or explosion in the plant made even worse by casualties. The other is an administrative or legal disaster. This could be a tax problem or worse like having been determined to be out of EPA regulatory compliance for a chemical release into the environment or worker exposure over time. EPA fines are levied per day per violation.

In my view, the USA began ossifying many years ago in regulatory paralysis in much the same way the EU or Japan has.  The combination of business risk aversion along with the popular sport of outsourcing our means of production only serves to accelerate the de-industrialization of the USA and the EU. At present there is some effort by the semiconductor manufacturers and others to repatriate manufacturing back to the US out of fear of foreign governments using strategic trade regulation as a competitive cudgel.

What can one reasonably do? Consider even if regulations could be softened, this could take a long time. Until such time as there is a change in regulation, it is best to knuckle under willingly. First on the list is to just be compliant with regulations. Even an excellent argument against an “unjust” regulation enforced by an agency will get you nowhere because regulators are legally required to enforce the regulations and fine violators. If you are facing a regulatory judgement, it is well worth having a lawyer who specializes in that area of the law.

Accepting a harsh judgement on your record can possibly hurt you in the future by having a history of serious earlier infractions. A lawyer can search the case law and possibly find a lesser judgement or better interpretation of the regulations. Avoid at all costs the possibility of being found a repeat violator in some future court action. There could be extenuating circumstances that should be taken into account, but this is the lawyer’s domain and is no place for amateurs.

Fiat Lux

In the chemical industry we have regulatory specialists and EH&S departments who keep on top of the regulations and are responsible for maintaining timely compliance. They help keep the doors open and should be appreciated. That said, executives lurking in the C-Suite should be at least conversant in labor and environmental regulation to the point where they know to get advice before issuing directions relating to this.

Note: Obviously I’m not a damned lawyer and my words should not be construed as actual legal advice. I am simply recollecting learnings from my experiences.

Chemical Emergencies and Safety Data Sheets in Education

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Note: Below is a quick safety brain-dump from a career in academic chemistry labs and chemical manufacturing facilities. It is not meant to be an unabridged guide to lab safety. Look elsewhere for that. it is easy to overlook Safety Data Sheets that come with chemical purchases.

At some time in their chemistry education the student should have had a good look at the chemical Safety Data Sheet or SDS for the chemicals and solvents they are using. While not necessarily very informative in terms of reaction chemistry, these documents are taken very seriously by many groups who can/will have an impact on your chemistry career and safety. Regardless of your walking-around-knowledge about a chemical substance, you should understand that the people who respond to emergency calls for a chemical incident will place a high reliance on what is disclosed on an SDS. A student who is connected with an incident won’t be the first point of contact when the fire department or ambulance arrives and wants information. In fact, it is highly unlikely that a student will ever have direct contact with a responder unless it is with an EMT.

Know where the SDS folder is. It may be in print or online.

When emergency responders arrive at the scene of your chemical incident, they will have protocols built into a strict chain of command. All information will pass through the responder’s single point of contact. The fire fighter with the fire hose is not the person you should try to communicate with. Information regarding the incident must be communicated up the chain of command from your site incident commander. The person responsible for the lab should know who that is. The staff at the incident site (your college) will also have protocols built onto a chain of command. Again, “ideally” the incident commander at the incident site will ask for information from others on the site regarding details on the event including the headcount (!) and communicate it to the incident commander of the responders. This is done to avoid confusing the responders with contradictory or useless information. Do not flood the responders with extraneous information. Don’t speak in jargon. If there are important points like “it’s a potassium fire”, pass it along. If there are special hazards like compressed hydrogen cylinders present, they’d like to know that too. Answer their questions then step back and let them do their job.

When responders arrive at the scene of a chemical incident, the first question they will ask is if everyone is accounted for. If everyone is accounted for, they will not risk their lives in the emergency response. However, if there are people unaccounted for or known to be trapped in a dangerous place or incapacitated, the responders will take greater chances with their own safety to rescue the victims. They will act to minimize property damage only if it can be done without risk to life and limb. Nobody wants to die saving property.

College chemistry departments that I have been involved with have had a flat policy of evacuating everyone from the building and congregating them at a defined location in response to an alarm. That way there is at least some reasonable chance that an accurate head count can be made. If technical advice is needed, faculty connected with the incident site should be consulted. The college will have an Environmental Health and Safety (EH&S) group or person who presumably will take charge of the incident on the incident side. The leader of EH&S should be informed of any hazards unique to the substance of concern if there is no SDS. Let them communicate with the responders. Generally, we chemists help most when we keep out of the way.

College chemistry departments are famous for housing one-of-a-kind chemical substances in poorly labeled bottles in faculty labs. These substances almost never have any kind of safety information other than perhaps cautionary advice like “don’t get it in your eye.” Luckily, university research typically uses small quantities of most substances except perhaps for solvents. Solvents can easily be present at multiples of 20 liters. These large cans are properly kept in a flammables cabinet. While research quantities may not represent a large fire hazard initially, there could easily be enough to poison someone. When you get to the hospital, the ER folks will have to figure out what to do with your sorry ass lying there poisoned by your own one-of-a-kind hazardous material.

In principle, the professor in charge of a chemistry research lab should be responsible for keeping an inventory of all chemicals including research substances sitting on the shelf. Purchased chemicals always have an SDS shipped with them. These documents should be filed in a well-known location and available to EH&S and responders.

The chemistry stockroom is a special location. Chemicals are commonly present at what an academic might call “bulk” scale, namely 100 to 1000 grams for solids and numerous 20 L solvent cans. The number of kg of combustibles and flammables per square meter of floor space is higher here. The stockroom manager should have a collection of SDS documents on file available to responders.

Right or wrong, people positively correlate the degree of hazard to the nastiness of an odor. Emergency responders are no different. This is another reason why it is critical for them to have an SDS. People need to adjust their risk exposure to the hazard present as defined by an SDS. We all know that some substances that are bad actors actually have an odor that is not unpleasant for a short time, like phosgene. Regardless of this imperfect correlation, if you can smell it, you are getting it in you and this is to be avoided. Inhalation is an important route of exposure.

In grad school we had an incident where a grad student dropped a bottle in a stairwell (!) with a few grams of a transition group metal complex having a cyclooctadiene (COD) ligand on it. Enough COD was released into the stairwell to badly stink it up. They didn’t know if it was an actual chemical hazard or not, so they pulled the fire alarm handle. The Hazardous Material wagon showed up right next to 50-60 chemistry professors, postdocs, and grad students. The responders were told what happened and with what, so they dutifully tried to find information on the hazards in their many manuals. They did not find anything.

They had 50-60 chemists within spitting distance but didn’t ask us any questions. This is because they are trained to respond as they did. This was a one-off research sample of a few grams but it had an obnoxious smell with unknown hazards. Finally they sent in some guys in SCBA gear and swept up the several grams of substance and set up a fan for ventilation. Don’t be surprised if the responders don’t have special tricks up their sleeves for your chemical event. They can’t anticipate every kind of chemical incident.

HazMat Team. Credit: https://en.wikipedia.org/wiki/Hazardous_materials_apparatus

Long story short, both the responders and the chemists didn’t have any special techniques tailor made for this substance. There was not evident pyrophoricity or gas generation. It was a dry sample so no flammable liquids to contend with. The responders used maximum PPE and practiced good chemical hygiene in the small clean up. Case closed.

An SDS is required for shippers as well. It shows them how to placard their vehicles according to the hazards. Emergency responders need to see the SDS in order to safely respond to an overturned 18-wheeler in the road or to a spill on a loading dock. It could also be that the captain of container ship wants to know precisely what kind of hazardous materials are visiting his/her ship.

Finally, an SDS should be written by a professional trained to do it properly. By properly I mean by someone who understands enough about regulatory toxicology, emergency response, relevant physicochemical properties, hazard and precautionary statements and shipping regulations to provide responders with enough information to respond to an incident. Here, incident means an unexpected release with possible exposure to people, a release into the environment or a fire or possible explosion.

In my world, the word “accident” isn’t used so much anymore. With the advent process hazard analysis (PHA) required by OSHA under Process Safety Management prior to the startup of a process, potential hazards and dangers are anticipated by a group of experienced experts and adjusted for. So, it is getting harder to have an unexpected event. “Accident” is being replaced with the word “incident.”

Toxicology is a specialty concerned with poisons. Regulatory toxicology refers to the field where measurements and models are used to define where a substances belongs in the many layers of applicable regulations. Toxicity is manifested in many ways with many consequences and each way is categorized into levels of severity. There is acute toxicity and there is chronic toxicity. Know the difference. That said, dose and exposure are two different things. Exposure relates to the presence of external toxicants, i.e., ppm in water or micrograms per cubic meter of air. Dose relates to the amount of toxicant entering the body based on the exposure time in the presence of a toxicant and the route of entry.

An SDS uses signal words like “Caution”, Warning”, or “Danger”. A particular standard test is needed to narrow down the type and magnitude of the toxicity. The figure below from the GHS shows the thresholds for categorization of Acute Toxicity.

Credit: Globally Harmonized System of Classification and Labeling of Chemicals.

Hazard and precautionary statements are important for an SDS. Rather than having everybody dreaming up their own hazard descriptions and precautions, this has been standardized into agreed upon language. Among other sources, Sigma-Aldrich has a handy list of Hazard Statements and Precautionary Statements available online.

Regulatory toxicology is very much a quantitative science enmeshed with a web of regulations. The EPA for instance does modeling of human health and environmental risks based on quantitative exposure or release inputs. Without toxicological and industrial hygiene testing data, they may fall back on model substances and default, worst case inputs to their models. In reality the certain hazard warnings you see on an SDS may or may not be based on actual measurement. The EPA can require that certain hazard statements be put on a given SDS based on their assessment of risk using models or actual data.

To be clear, hazard information reported on an SDS are considered gospel to emergency responders. Chemists of all stripes should be conversant with Safety Data Sheets and have a look at them the next time a chemical arrives. Your lab or facility should have a central location for SDS documents, paper or electronic.

In the handling and storage of chemicals, some thought should be given as to how a non-chemist would deal with a chemical spill. Is the container labeled with a CAS number or a proper name rather than just a structure? A proper name or CAS # could lead someone to an SDS. Is there an HMIS or other hazard warning label? There are many tens of thousands of substances that are either a clear, colorless or amber liquid or a colorless solid. If not for the sake of emergency responders then for the poor sods in EH&S who will likely have to dispose of the stuff when you are long gone. Storing chemicals, liquids especially, with some kind of secondary containment is always a plus. Keep the number of kilograms of combustibles and flammables in the lab to a minimum. A localized fire is better than a fire that quickly spreads to the clutter on the benchtop or the floor.

On the Release of Hazardous Energy for Chemists

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This post is an update of a post I wrote on Mole-Day of 2011. It is a brain dump that summarizes much of what I’ve learned about dealing with potentially explosive chemicals in the manufacturing environment. Very few chemists actually have to deal with explosive chemicals in their work activities. It is actually quite uncommon. No doubt some important considerations have been left out and for that I apologize.

The Prime Directive: If you choose to bring in or make a chemical substance in your facility, you must develop in-house expertise in the safe handling and use of that substance. Do not expect to rely on outside expertise for it’s safe use. Always strive to build in-house expertise in regard to chemical properties and safety- never farm this out to consultants. This includes proper engineering and broad knowledge of reactive chemical hazards.

Safety has a substantial psychological component. You can build into a chemical manufacturing process extensive engineering and administrative controls for safe operation. These layers of control are concrete and definable. What is fuzzy, however, is the matter of how people behave. In particular, I’m thinking of getting people to behave in a particular way over the long haul. Keeping people operating safely over long periods of time where no adverse events happen poses special problems. Especially in regard to low frequency, high consequence events. Cutting corners and improper use of PPE is not uncommon and should be expected. Something expected can be watched for continuously.

In safety training I mention that handling a hazardous material is like handling a rattle snake. You have to exercise the due caution every single time you pick up that snake. You do not accumulate and bank safety credits for previous safe handling. Everybody understands this already at some level. But the possibility of drift in safety practice over time needs to be emphasized.

The best strategy I know of besides complete process automation is recurrent safety training along with vigilant management. Successful safety management requires proper supervision by alert supervisors. Management by walking around helps with this. Well written process instructions that anticipate practical problems are essential. Holding people accountable for following Standard Operating Procedures is critical. Working conditions conducive to focus are always good. Operational rotation with may be helpful.

In chemical safety, the biggest worry is typically the potential for an explosion. What should you do if a raw material or product in a process may be explosive or has explosive features on the molecule? Good question. First, someone in the R&D chain of command should have knowledge of the list of known explosophores. It’s not a big list. PhD chemists in R&D should know this anyway. Explosive molecules have certain chemical bonds that are weakest and are known as “trigger bonds“. It is thought that the rupture of these trigger bonds initiates explosive decomposition of the substance.

Just because a material has explosive properties does not automatically disqualify it for use. Azides and nitro compounds are used safely every day. But, to use a chemical safely you must accumulate some knowledge on the type and magnitude of stimulus that is required to give a hazardous release of energy.

For any given hazard, it is my personal policy to learn as much about the nature of the hazard at the chemical and bulk level as I can. I believe that it is important to know more about something than what is immediately called for. That is the difference between education and training. This is how you build expertise.

Some comments on the release of hazardous energy. Hazardous energy is that energy which, if released in an uncontrolled way, can result in harm to people or equipment.  This energy may be stored in a compressed spring, a tank of compressed gas, the stable chemical bonds of a flammable material, the unstable chemical bonds of an explosive material, or as an explosive mixture of air and fuel. A good old fashioned pool fire is a release of hazardous energy as well. Radiant energy heating from a pool fire can easily and rapidly accelerate nearby materials past the ignition point. Good housekeeping goes a long way towards preventing the spread of fires.

Applying and accumulating energy in large quantities is common and actually necessary in many process activities. In chemical processing, heat energy may be applied to chemical reactions. Commonly, heat is released from chemical reactions at some level ranging from minimal to large. The rate of heat evolution in common chemical reactions can be simply and reliably managed by controlling the temperature or rate of addition of reactants where two reactants are necessary. However, reactions do not always evolve significant power output immediately on mixing of the reactants.

Induction periods are potentially dangerous and must be identified prior to scale up. The appearance of an exotherm very early in a feed operation is a good indication that the reaction has begun. However, a thermogram from a reaction calorimeter showing the temperature and power output (watts) versus the feed mass will indicate if the reaction is slow and accumulation of reagent (energy) is occurring. This can be teased out early by adding a small shot of reactant feed (a few %) and watching the power profile. The ideal profile is where the power output starts promptly, peaks and then promptly decays to baseline. This is a good indicator of the absence of accumulation. Generally, the kinetics are most favorable at the beginning of the reagent feed and taper off to zero as reactants are consumed. Some accumulation is usually tolerable from the heat load perspective. This is a good thing because a thermogram showing some accumulation could lead to an unnecessarily long feed time. A reaction calorimeter can give the peak wattage per kilogram of reaction mass. An engineer should be able to estimate the maximum controllable heat flux for a given reactor. Without being too specific, it is in the range of several tens of watts per kg of reaction mass according to one reference I know.

There are explosive materials and there are explosive conditions. If one places the components of the fire triangle into a confined space, what may have been simple flammability in open air is now the makings of an explosion. Explosive materials have two legs of the fire triangle built into the molecule- the oxidizer and the fuel separated by only nanometers. However, the composition of the explosive itself may not produce a balanced reduction/oxidation reaction. The oxygen balance is a easily calculated number that will indicate whether or not there is an excess or deficit of oxygen in an explosive substance. For example, ammonium nitrate has a 20 % excess of oxygen. Fuel oil can be added to bring the fuel/oxidizer ratio into redox balance. This mixture is referred to as ANFO.

In a chemical explosion, heat and increasing pressure can do PV work on the contents and containment. Minimally, the outcome will be an overpressure with perhaps the blowing of a rupture disk on a reactor. In another situation, the equipment may blow apart and send fragments flying away at high speed with an expanding fireball.

There is a particular type of explosive behavior called detonation. Detonation is a variety of explosive behavior that is characterized by the generation and propagation of a high velocity shock through a material. A shock is a high velocity compression wave which begins at the point of initiation and propagates throughout the bulk mass of explosive material.  Interestingly, because it is a wave, it can be manipulated somewhat by reflection and refraction. This is the basis for explosive lensing and shaped charges. It is characteristic of detonations to produce shredded metal components. Detonations have a very large rate of pressure rise, dP/dt. The magnitude of dust explosions is commonly performed by a few commercial test labs out there. One of the important test results is the Kst value showing the magnitude of the explosive force.

Detonable materials may be subject to geometry constraints that limit the propagation of the shock. A cylinder of explosive material may or may not propagate a detonation wave depending on the diameter. Some materials are relatively insensitive to the shape and thickness. A film of nitroglycerin will easily propagate as will a slender filling of PETN in detonation cord. But these compounds are for munitions makers, not custom or fine chemical manufacturers. The point is that explosability and detonability is rather more complex than one might realize. Therefore, it is important to do a variety of tests on a material suspected of explosability. The type and magnitude of stimulus necessary to produce an explosion must be understood for safe handling and shipping.

A characteristic of detonable explosives is the ability to propagate a shock through the bulk of the explosive material.  However, this ability may depend upon the geometry of the material, the shock velocity, and the purity of the explosive itself. There are other parameters as well. Marginally detonable materials may lose critical energy if the shape of the charge provides enough surface area for loss of energy.  

Explosive substances have functional groups that are the locus of their explosibility. A functional group related to the initiation of explosive behavior, called an explosophore, is needed to give a molecule explosability. Obvious explosophores include azide, nitro, nitroesters, nitrate salts, perchlorates, fulminates, diazo compounds, peroxides, picrates and styphnates, and certain hydrazine moieties. Other explosophores include the hydroxylamino group. HOBt, a triazole analog of hydroxyamine,  hydroxybenzotriazole, has injured people, destroyed reactors and caused serious damage to facilities. Anhydrous hydroxylamine has been the source of a few plant explosions as well. It is possible to run a process for years and never cross the line to runaway as was the case for these substances.

Let’s go back to the original question of this essay. What do you do if you find that a raw material or a product is explosive? The first thing to do is collect all available information on the properties of the substance. In a business organization, upper management must be engaged immediately since the handling of such materials involves the assumption of risk profiles beyond that expected.

At this point, an evaluation must be made in relation to the value of the product in your business model vs the magnitude of the risk. Dow’s Fire and Explosion Index is one place to start. This methodology attempts to quantify and weight the risks of a particular scenario. A range of numbers are possible and a ranking of risk magnitude can be obtained therein. It is then possible to compare the risk ranking to a risk policy schedule generated beforehand by management. The intent is to quantify the risk against a scale already settled upon for easier decision making. A problem with this approach is that it requires numerical values for risk which might be difficult to come by.

But even before such a risk ranking can be made, it is necessary to understand the type and magnitude of stimulus needed to elicit a release of hazardous energy. A good place to start is with a DSC thermogram and a TGA profile. These are easy and relatively inexpensive. A DSC thermogram will indicate onset temperature at a given temperature ramp rate and energy release data as a first pass. Low onset temperature and high energy release is least desirable. High onset temperature and/or low exothermicity is most desirable.

A DSC thermogram copied from Mettler-Toledo. MT makes great equipment. Exotherm is positive deflection of the curve and the endotherm is negative. https://www.mt.com/us/en/home/library/on-demand-webinars/lab-analytical-instruments/DSC_TA.html

What is more difficult to come to a decision point on is the scenario where there is relatively high temperature onset and high exothermicity.  Inevitably, the argument will be made that operating temperatures will be far below the onset temp and that a hazardous condition may be avoided by simply putting controls on processing temperatures. While there is some value to this, here is where we find that simple DSC data alone may be inadequate for validating safe operating conditions.

Onset temperatures are not inherent physical properties. Onset temperatures are kinetic epiphenomena that are dependent on the sensitivity of the instrument, sample quality, the Cp of both the sample and the crucible, and the rate of temperature rise. What may be needed once an indication of high energy release is indicated by the DSC is a determination of time to maximum rate (TMS). While this can be done with special techniques in the DSC (i.e., AKTS), TMR data may be calculated from 4 DSC scans at different rates, or it may be determined from Accelerated Rate Calorimetry, or ARC testing. Arc testing gives time, temp, and pressure profiles that DSC cannot give. ARC also gives an indication of non-classical liquid/vapour behavior that is useful. ARC testing can indicate the generation of non-condensable gases in the decomposition profile which is good to know.

Time to maximum rate is measured in time at a specified temperature. Many people consider that a TMR of 24 hours at the process temperature is a minimum threshold for operational safety. Others might advise 24 hours 50 or 100 C above the maximum operational temperature. If you contemplate using this parameter, it is critical to get testing from a professional lab for a time at a particular temperature. This kind of test will produce a formula that you can calculate TMR values at a given temperature. Bear in mind, however, that no outside safety consultant will tell you what you must do for liability reasons. You must develop enough in-house expertise to make this decision for yourself.

The standard tiered test protocol for DOT classification is a good place to start for acquiring data on explosive properties.  Several companies do this testing and give ratings. There are levels of testing applied based on the result of what the lower series tests show. Series 1 and 2 are minimally what can be done to flesh out the effects of basic stimuli.  What you get from the results of Series 1, 2, and 3 are a general indication of explosibilty and detonability, as well as sensitivity to impact and friction. In addition, tests for sensitivity to electric discharge and dust explosion parameters should be performed as well. 

Effect types on a sample container from a Koenen test of explosive material. https://www.osti.gov/servlets/purl/1505408

The card gap test, Konen test, and time-pressure test will give a good picture of explosive behavior. The Konen test indicates whether or not extreme heating can cause an explosion sufficient to fragment a container with a small hole in it.

Figure from https://www.osti.gov/servlets/purl/1465274

BOM or BAM impact testing will indicate sensitivity to impact stimulus. Friction testing gives threshold data for friction sensitivity.

ESD sensitivity testing gives threshold data for visible effects of static discharge on the test material. Positive results include discoloration, smoking, flame, explosive report, etc.

Once the data is in hand, it is necessary to sift through it and make some business decisions. There is rarely a clear line on the ground to indicate what to do unless there is already a policy on decision making here. What testing results will indicate is what kind of stimulus is necessary to give a positive result with a particular test. It is up to your in-house experts and management to decide the likelihood of exposing the material to a particular stimulus. Will it be possible to engineer away the risk or diminish it to an acceptable level? The real question for the company is whether or not the risk of processing with the material is worth the reward. Everyone will have an opinion.

The key activity is to consider where in the process an unsafe stimulus may be applied to the material. If it is thermally sensitive in the range of heating utilities, then layers of protection guarding against overheating must be put in place. Layers of protection should include multiple engineering and administrative layers.  Every layer is like a piece of Swiss cheese. The idea is to prevent the holes in the cheese from aligning. 

If the material is impact or friction sensitive, then measures to guard against these stimuli must be put in place. For solids handling, this can be problematic. It might be that preparing the material as a solution is needed for minimum solids handling.

If the material is detonable, then all forms of stimulus must be guarded against unless you have specific knowledge that indicates otherwise. Furthermore, a safety study on storage should be performed. Segregation of explosable or detonable materials in storage will work towards decoupling of energy transfer during an incident.  By segregating such materials, it is possible to minimize the adverse effects of fire and explosion to the rest of the facility.

With explosive materials, electrostatic safety is very important. All handling of explosable solids should involve provisions for the suppression of electrostatic charge generation and accumulation. A discharge of static energy in bulk solid material is a good way to initiate runaway decomposition of an energetic material. Unfortunately, some explosive substances may not require the oxygen leg of the fire triangle so, in this case, inerting with nitrogen won’t be preventative.

Safe practices involving energetic materials require an understanding the cause and effect of stimulus on the materials themselves. This is of necessity a data and knowledge driven activity. Handwaving arguments should also be suppressed in favor of data-driven analysis.

Chemical safety as social science

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Chemical manufacturing safety is challenging to oversee consistently over time. A given manufacturing facility has many kinds of hazards, some common and some specific to plant activity. Specialized operations will produce hazards that manifest in ways ranging from obvious to obscure to counterintuitive. For those tasked with keeping operations free from injuries and mishaps, the hard part may be to keep everyone vigilant constantly.

I often compare safe practices to the handling of a rattle snake. Every time you pick up that snake, you have to be just as careful as the last time. Over time you may learn to predict or anticipate threatening snake behaviors, but you do not get to bank safety credits for past cautious behavior. Furthermore, it is necessary for you to change some of your basic behaviors around the rattler. For instance, you may want to alter your posture when standing near the snake so, if you lose your balance, you fall away from the snake, not onto it. Or, you may decide to bring the snake out only when there is not a crowd around you for fear of spooking the animal. A wrangler can cite many techniques to adopt when handling this venomous creature.

My views of safety policy and practices have evolved over time. In the academic and industrial lab facilities I have worked, safety policy varied from “don’t get hurt” to academic departmental policies with the unofficial “for god sakes don’t let a student get hurt” to highly professional facilities using “we reserve the right to dismiss you” if your accident involved a violation of policy. In these chemistry jobs I have functioned as a dairy processing lab chemist, student assistant, grad student, postdoc, assistant professor, chemical sales manager, senior scientist and process safety chemist. There has been some variety.

What allowed my successful navigation through these experiences with body parts intact? Skill from good training and a large shot of luck. And having been cautious by nature when it comes to hazardous energy and chemical hygiene doesn’t hurt.

In my estimation there is a large social/psychological component to safety anywhere. Safe operations in a chemical plant requires an alignment of behaviors that lead away from mishaps due to all manner of influences, predictable or otherwise. To oversee safety at a facility, one must use facts and the power of persuasion to convince people to behave in ways that might seem needless or unnatural. There is a large social component to safety. That said, the threat of dismissal doesn’t hurt.

In a US chemical plant, operational staff commonly undergo safety training on hiring and refresher training thereafter on a periodic basis. If an adverse event happens relevant staff may undergo a refresher training session as policy dictates. The range of safety topics will depend on the kind of activity happening at the facility.  Safety training has the goal of bringing and keeping staff up to par on recognition and prevention of some kind of undesired event that plays out as a near miss or an incident.

A core subject in chemical manufacturing facility is the matter of hazardous energy. Hazardous energy is manifested in numerous ways: High pressure, high temperature, electrostatic, rapid or runaway heat of reaction, compressed springs and energy of motion. Hazardous energy can emerge from the familiar and the unfamiliar.

Dangers emerging from “ordinary” hazards, i.e., the hazards everyone is accustomed to, can perhaps be most vexing. How does one convince people not to become complacent with familiar hazards, particularly those of low frequency high consequence?

Frequent training and thorough root cause analysis of actual incidents is probably the best approach to suppressing complacency. One need look no further than the military for an example. Military personnel undergo frequent training with an emphasis on situational awareness. A particular strength is the existence of protocols for many exigencies and the mandatory adherence to that protocol. The obvious problem of the military approach to training is that it is not aimed at producing material goods for a competitive market. Businesses cannot afford to lavish much downtime to training. Civilian safety training in business is conducted but at nothing like the frequency or scale that the military uses to maintain readiness.

A useful tool available to industrial safety is layer of protection analysis (LOP). There are companies that offer custom LOP services/instruction and outside assistance is often a good thing. Other resources exist as well. There are two kinds of layers- administrative and engineering. Administrative layers of protection include the process instruction document, various SOPs and work instructions, training as well as eyes-on active management. Engineering layers of protection refers to the equipment which protects against the effects of an excursion.  Each layer will have empty spaces where they are not protective. The idea is to lay down layers where the empty spaces do not overlap. Most would agree that engineering LOP are preferred over administrative LOP.

The terms “dangerous” and “hazardous” are often used interchangeably. I would argue that the word danger be reserved for the situation when all of the layers of protection around a hazard have been removed. This is an important distinction because our lives are filled with hazards that don’t fill us with dread fear. We tolerate this only because we contain hazards with layers of protection which prevent the consequences of the hazard. In order to keep working in an industrial setting, we all must come to terms with the contained hazards on site. Workers predisposed to chemophobia must become comfortable with the LOP in place, yet remain vigilant for uncontained hazards. The alternative for them is to work elsewhere.

Incidents should be followed closely by a Root Cause Analysis, RCA. There should be an SOP that specifies this action. With any luck, an expert conversation in the subject matter at hand will spark the insight of someone leading to the identification of failure modes related to the incident. The RCA will identify which dominoes fell in the event and will highlight the weak points and hopefully find the initiating event. Finding the incident initiating event is always a goal.

It is important to evaluate the existing LOP after the RCA and every effort should be made use the event to strengthen systems. The notion of LOP should be present early in the process of writing instructions for the manufacture of materials. Each batch or process instruction document should be critically evaluated and signed off by a variety of experienced people. This would include R&D chemists, chemists and engineers involved in process scaleup, Environmental, Health and Safety, production supervisors and plant managers. All can be reminded to evaluate the production document with LOPA in mind.

Inevitably, incidents and near misses stemming from unanticipated failure modes will occur. To provide added protection against the unexpected, imaginations need to be stimulated by conducting a PHA- Process Hazard Analysis. This must be done before a process is begun. It is a formal brainstorming session conducted by a committee of subject matter experts evaluating every step in a chemical process at the production scale for possible failure scenarios. These will be chemical, mechanical or safety systems related. In the PHA you ask the question: What happens if this component or action fails in the process? It is a detailed what-if map of the failure or event with potential consequences. Each potential consequence must be evaluated for risk and harm. Software is available to help people guide themselves through the process.

Finally, it should be noted that once the incident investigation is complete, learnings from the event should be applied going forward and archived where the results can be readily found.

Reactive Hazards Seminar

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One of the safety seminars I teach is on the general topic of reactive hazards. There is a bit of a challenge to this because the idea is to cultivate informed caution rather than allow broadband fear to rule. It is challenging because my class is generally populated with non-chemist plant operators or other support staff. Out in the world the word “chemical” is generally taken to be an epithet and indicative of some malign influence. We who work with chemicals are in a position to bear witness to the reality of chemistry in our lives and to speak calmly and reasonably about it, without crass cheerleading.

Here is how I look at this. There are hazards and there are dangers. A hazard is something that can cause harm if it was to be fully expressed by way of physical contact with people or certain objects, unbounded access to an ignition source, exposure to air, etc. A critical feature of the hazard definition is that there are layers of protection preventing undesired contact. Hazards can be contained. A contained hazard is safer to be around than an uncontained hazard.

An uncontained hazard is that which can cause harm without the interference of effective layers of protection. A hungry tiger in a cage is hazardous in that there is the potential for trouble if the cage is breached. Being openly exposed to that tiger is what I’ll call dangerous.

Likewise, a stable chemical in a bottle has a physical layer of protection around it. A policy on the use of that bottled chemical constitutes a concentric administrative layer of protection. The bottle sitting in a proper cabinet within a room with limited access has more layers of protection. The policy of selling that chemical only to qualified buyers is a further layer of protection.

Egg white to which has been added several drops of conc H2SO4 (bottom) and 50 % caustic (top). Two minutes have elapsed. The point of this demo is to show what might happed to a cornea on contact with these reagents. The clouding is irreversible. People remember demonstrations.

It is possible to work around contained hazards safely and most of us do this outside of work without giving it much thought. Hazardous energy is exploited by most of us in the form of moving automobiles, spinning jet turbines, rotating machinery of all kinds, compressed gases and springs, and flammable liquids. Safe operation around these hazards is crucial to the conduct of civilization right down to our daily lives.

It is very easy for experts to frighten the daylights out of people by an unfortunate choice of words or simply dwelling on the hazardous downside too much. Users of technology should always be versed in the good and bad elements as a matter of course.

Risk can be defined as probability times consequence. So, to reduce risk one can reduce probability, diminish undesired consequences, or both.  This is the purpose of LOPA, or Layers of Protection Analysis. LOPA can provide a quantitative basis for safety policy. The video below will explain.

https://youtu.be/L3kQ9DKHS5A

Designing for tolerable risk is something that all of us in industry must come to grips with.