Wednesday, December 12, 2007

Top Screen Questions: Flammable and Explosive Release Chemicals of Interest

In yesterday’s blog I discussed the Top Screen Questions for Toxic Release chemicals. Today we will look at the same thing for the two remaining Release chemical categories; Flammables and Explosives. Actually, this will be relatively easy since they both have the same sets of data requirements and they are simpler than those for Toxic Release chemicals.


The first area for these chemicals has the same layout as found in the Toxic Release chemical section. The first portion of this area of the Top Screen is identifying which chemicals the facility has (or has had in the last 60 days) on site at or above the STQ. The chemicals are listed alphabetically by chemical name. For each chemical there is a CAS number listed to aid in identification of the chemical of interest. There is a minimum concentration that must be equaled or exceeded for the chemical to be counted (only the actual amount of the chemical in a mixture not the entire mixture) in the STQ calculations. Finally there are check boxes to indicate if the listed chemical was present at or above the STQ. The default value is “No”, so the only chemicals that need to actually be marked are those that meet or exceed the STQ.


Where there were two questions at the end of this section for Toxic Release chemicals there is only a single question for each of these two Release chemicals. The question asks if you have marked every chemical that should have been marked; responses are yes or no, with the “No” box the default value. Even if no Toxic Release Chemicals of Interest were present on the facility at or above the STQ within the last 60 days a yes response is required to this question to signify that list has been evaluated.


The second section for these two Release chemicals is a combination of the second and third section for Toxic Release chemicals, with boxes for “Total On-Site Quantity” and “Quantity in AHQ”. The reason that DHS could combine these two sections is that thereis no requirement to calculate a Distance of Concern for either of these chemicals. 


The general rules for the calculations for the quantities for these two Release chemicals is generally the same as used for the Toxics with the exception of how the concentrations are used to calculate the amount of a mixture that will be included in either of these two quantities. For explosives the total amount of “A Commercial Grade” explosive (if it is sold as an explosive it is a commercial grade) is counted regardless of the concentration. For flammable mixtures, if the mixture is an NFPA 4 flammable the total quantity is counted regardless of the concentration. If the mixture is not an NFPA 4 flammable then only the actual amount of the chemical is counted.


There is a potential problem with the concentration rule for flammables. If a mixture that is a NFPA 4 flammable liquid contains two or more Flammable Release chemicals at concentrations of more than 1% the total amount of that chemical will have to be counted for each of the listed chemicals. This will make the facility look like a higher hazard than it actually is. I do not see how this can be appropriately captured in the Top Screen. My only suggestion is that any facility that has this happen in their Top Screen and is notified that it is designated a High-Risk Facility should contact DHS directly to see if a more appropriate accounting of their inventory would reduce their risk rating.


There is one other exemption to the standard rules for counting the amount of Flammable Release chemicals, propane. DHS has elected to treat propane in a unique manner (see my blog: The politics behind Appendix A propane rules). Propane tanks that hold less than 10,000 lbs are not to be counted in the propane totals. There is nothing in the Top Screen that says this but it is covered in Section 27.203(b)(3). Hopefully there will be detailed instructions in the Top Screen User’s Manual when it is eventually published.

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