Incompatible materials

Incompatibility is a relationship between chemicals, not a property of one alone. Acids and bases release heat when mixed; oxidizers and fuels can ignite; bleach mixed with ammonia or with acids can release toxic gas; water-reactive metals react with moisture. Knowing a product is hazardous alone is not enough: you must also know what it must stay away from.

Section 10 of the SDS is the standard source, usually listing specific chemicals or classes such as strong acids, strong bases, oxidizing agents, reducing agents, metals or moisture. The list varies by supplier, and it is often short, so a chemical hygiene plan should add broader segregation rules.

Segregation is the main control. Group storage by hazard class, not alphabetically, and separate groups using distance, cabinets or barriers. Secondary containment trays can stop leaks from two neighboring containers from meeting. Never assume a sealed container is safe if it might leak or fail in a fire or earthquake.

Mixing mistakes also occur outside storage: in waste containers, during cleaning, in drain lines and in spill cleanup. Employees should know not to combine products and to use only the cleaning agents approved for the job.