The DOT ERG identifies chemicals as being shipped “inhibited” or “stabilized” and have a “P” listed with their guide number meaning that the chemical can polymerize. These inhibitors are TIME and TEMPERATURE dependent! The inhibitors can be tested and more inhibitor added if necessary, albeit VERY RISKY once the reaction has begun AND the fact that these inhibitors are not something First Responders have readily available. This week we learned that the inhibitor used in styrene, UN2055, is 10 to 50 ppm of tertiary butyl catechol (4-tertiary-butyl-catechol), with the higher concentration for higher storage temperatures. Here is a listing of other chemicals that can polymerize as the Styrene did in Selkirk, NY this week.