Sunday, August 25, 2013

Reader Email – Reactive Chemistry

I received an interesting email from a reader, Jim, this week about my earlier posting on reactive chemistry and the President’s executive order on “Improving Chemical Facility Safety and Security” (EO 13650). He pointed out a much more common problem of reactive chemistry that I had overlooked that could be considered by the Chemical Facility Safety and Security Working Group while addressing the requirements of §6(c).

Incompatible Chemicals

The reactive chemicals that the reader addresses is the most basic type of chemical hazard, incompatible chemicals; chemicals that because of their most basic nature should not be allowed to come into contact with each other outside of the most controlled chemical process. We are talking things as basic and acids and bases, oxidizers and flammables, and monomers and initiators.

I missed this in my earlier discussion because to me, as chemical professional, this is the most basic component of chemical safety that I almost don’t consciously think about this as an issue. Which is, of course, why it is such a common problem. To be fair, every process hazard analysis (PHA) that I have ever participated in has addressed this issue for the chemicals under review. Jim suggests that the review should be extended to all chemicals at the facility that could come into physical contact with one another.

Reactivity Matrix

Jim suggests the establishment of a reactivity matrix. In its simplest form this would be a spread sheet listing of every chemical in the facility. Each chemical would be listed once on both the horizontal and vertical axis of the spread sheet. At each intersecting cell an entry would be placed that would describe the consequences of mixing the two chemicals. The listing would be (my terms not Jim’s):

• No reaction – quality issues are not a safety consideration;
• To be Avoided – A reaction occurs but, no heat or gasses are evolved, no toxic byproducts are produced, and the resulting material would not be hazardous waste;
• Administrative Controls Required – Minimal heat or non-flammable gasses may be evolved, but not enough to raise pressure in a sealed container with 5% headspace by 1 psig, toxic byproducts may be produced but do not require an increase in personal protective equipment to protect employees against exposure when handling, or waste may require disposal as hazardous waste; or
• Physical Controls Required – Will evolve heat or gasses that will raise pressure in a sealed container with 5% headspace by more than 1 psig, will evolve flammable gasses, or will produce toxic byproducts that will require an increase in personal protective equipment to handle.

Administrative controls are procedures and policies that control when and where such mixing of chemicals may take place. Any reaction requiring administrative controls should require that a HAZOP be performed to review and document those controls.

Physical controls are devices that prevent or control the mixing of the chemicals involved. Any reaction requiring physical controls should require that a PHA be performed to review and document those controls.

Information Availability

Jim makes the point that for most chemical combinations there will be no need for any basic research to take place to make a determination what the reaction label would be for most common chemicals. The information is generally available in the chemical literature. Unfortunately, there are many facilities that use dangerous chemicals that do not have anyone on staff qualified to conduct and interpret a literature search in this area.

A relatively simple and low cost alternative would be to have a research organization like NIST publish a database covering the most common industrial chemicals in use in the United States. The database could be set up to produce a matrix spread sheet by simply selecting the various chemicals that a facility had on site. The facility would only have to fill in the blanks for any chemicals or combination of chemicals not found in the database.


Which federal agency would be responsible for enforcing this matrix? Well it would depend on the degree of hazard produced by the reactions. Facilities with reactions in only the first two categories (‘No Reaction” and ‘To Be Avoided’) would not generally be regulated for the chemical reactivity matrix. Facilities that have reactions that fall into the last two categories (‘Administrative Controls Required’ or ‘Physical Controls Required) would be required to do a worst case scenario analysis. If that analysis shows no off-site hazards (beyond disposal of hazardous waste) then PSM would be the only regulations addressing the reactivity matrix that the facility would be concerned with. If there were potential off-site consequences the RMP program would be involved and the CFATS people (keeping in mind the existing exemptions) would be notified so that a risk of terrorist attack based upon the reactivity matrix could be assessed.

Major Political Problem

While this all sounds very simple, there is a serious political impediment to this being adopted. We routinely accept chemical reaction risks in our everyday lives. In our kitchens we store incompatible chemicals under the sink, ammonia cleaners and bleach, peroxide and rubbing alcohol being the two common examples. Will every household have to conduct a HAZOP when they buy these materials? Not likely. We use pool chemicals that will violently react and produce chlorine gas. Will every pool cleaning company have to have people on staff to conduct a PHA? It would shut most of them down. Hell, even Mentos® and Coca-Cola® would be regulated under this scheme.

This is one of the reasons that regulators have been so reluctant to try to add reactive chemicals to their chemical safety programs. How do you define realistic safety programs that do not unnecessarily interfere with how people live their lives? At what level in the supply chain should chemical safety controls come into play? Certainly not at the consumer level for all but the most serious hazards. Will the local grocery store have to implement physical controls to prevent the mixing of cleaners? Will the regional warehouse?  These are all political questions, not safety questions, that will have to be addressed.

One way around this is to apply the chemical reaction matrix requirement only to current PSM and RMP covered facilities. This would certainly expand the scope of the current rules, but would not bring any new facilities into the regulatory scheme. This would probably not have any quantum leap in chemical facility safety, but it would cause at least some facilities to take a harder look at chemical reactivity and that would certainly be a good thing.

In any case, this is one approach that the Working Group could take in addressing the requirements for their November 5th review of reactive chemistry required by §6(c) of EO 13650.

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