Decomposition Hazard

Overheating or contamination of persulfates can lead to a runaway decomposition. The persulfate salt will begin to effervesce with an acid-like odor. Persulfates decompose to form solid sulfate salts and emit noxious fog or fumes of SOx and NOx.

This decomposition may form a high temperature melt. The material will flow like magma and may ignite nearby combustible materials such as wood or paper. Oxygen produced by persulfate decomposition can increase the intensity of the fire. 

The only way to halt a decomposition event is to apply LARGE quantities of water to the reacting material. Eight pounds of water per pound of decomposing materials is recommended, but no less than two pounds of water should be applied. Insufficient amounts of water will intensify the reaction and increase the acid mist concentration. 

Please note that carbon dioxide (CO2) or other gas-filled extinguishers will have NO effect on decomposing persulfate. The use of water as an extinguishing agent is emphasized. Control of the melt and firefighting efforts are enhanced if persulfates are stored within containment areas.

Persulfate decomposition will require emergency responders wearing full protective rubber clothing, face and head protection, plus self-contained breathing apparatus (SCBA).

Decomposition Prevention

Observe the following precautions to prevent decomposition:

Do not expose persulfates or their containers to moisture. Moisture significantly lowers the decomposition temperature.

Do not store persulfates near incompatible materials such as reducing agents, acids, bases, halide salt solutions, organics, ammoniacal solutions, alkaline cleansers, or other oxidizers. These materials can initiate decomposition.

Do not store near point sources of heat such as steam pipes, electrical appliances, heating vents, gas flames, welding sparks, or radiant heaters. Do not store at ambient temperatures above 113°F or 45°C. 

Do not return spilled or unused portions of persulfates to the original container. Dirt, metal, moisture, or other contaminants can induce the decomposition of persulfates.

Do not cross-contaminate with scoops, cups, or stirrers that may have been exposed to or used with other chemicals. Use only dedicated clean, dry plastic or stainless steel scoops and utensils for transfer.

Do not grind or dry mix in equipment or machines that develop frictional heat.