Supplies left between treatments or seasons still have storage requirements. The Virginia Department of Health calls for a cool, dry location away from direct sunlight, with good ventilation. It also specifies original containers, proper labels and containers that are neither damaged nor leaking.
Why moisture matters
The U.S. Chemical Safety Board describes chlorinated isocyanurates as sanitisers used in swimming pools, spas and industrial water applications because of their available chlorine content. That high chlorine content can also make the compounds hazardous to handle and store. CSB says heat or small amounts of water or moisture can trigger dangerous decomposition in oxidisers such as these. The decomposition can release toxic vapours and produce intense heat, with the potential for fires or explosions.
Virginia's guidance names several ways stored chemicals can become wet: rainwater, leaks, wet floors, sprinklers and high humidity. A cool, dry, well-ventilated area is also the storage setting specified by CSB for chlorinated isocyanurates.
Original containers and separate scoops
The Virginia Department of Health's pool chemical guidance says chemicals belong in their original containers and that containers must not be reused. It also calls for proper labels and containers in good condition, without damage, breakage or leaks. The agency also directs attention to the manufacturer's instructions on the label.
The same guidance assigns tools to individual chemicals. A scoop used for one chemical is not shared with another, because sharing the tool can cause a reaction.
Old and fresh supplies
Virginia explains that chemicals degrade as they get old and their chemical composition changes. Old chemicals can react when mixed with fresh chemicals, even if both containers are labelled as the same kind. The agency therefore warns against mixing the older and fresher supplies.
Liquids and dry chemicals
Virginia says liquid chemicals must never be stored above dry chemicals.
The surrounding storage space
Virginia's guidance also excludes other equipment from chemical storage, giving lawn mowers and leaf blowers as examples. It calls for a well-ventilated area, away from direct sunlight, and prohibits smoking in chemical storage areas or while using chemicals.
A warehouse fire and the moisture warning
In its investigation of a chemical-storage warehouse fire, the U.S. Chemical Safety Board found that water from a corroded sprinkler reached highly reactive pool-treatment chemicals. The contact caused a chemical reaction, off-gassing, significant heat and fires. CSB reports that the resulting smoke contained chlorine, hydrogen chloride, bromine and other substances.