Squeamishness is one of the most common, albeit intangible residues of subsiding flood waters, and it is a sentiment that has been widely shared in many Canadian cities and towns this year.

Building owners and managers faced with the cleanup of deluged and damaged properties may be understandably anxious to scrub the areas where non-potable – and often downright disgusting – water has stood. Nevertheless, decontamination must be approached with a knowledge of chemistry so that the cleaning chemicals do not cause even greater and more immediate hazards.

Any mixture of bleach and ammonia creates volatile and dangerous toxic vapours that were the basis of the mustard gas used in the First World War. Inhalation can cause coughing, bronchitis and long-term respiratory harm. Symptoms typically appear one to six hours after exposure.

Bleach is a very effective cleaning agent, with a long history of use in many applications, but it must be used correctly, especially if other cleaning chemicals are present. Likewise, hydrogen peroxide is an environmentally-friendly cleaner but it must be used on its own or only mixed with water. Mixing different brands of the same type of product should also be avoided because the cleaners may have different formulations or ingredients that react when combined.

Dangerous cleaning agent combinations include:

• Bleach and vinegar (vinegar is a form of acid);
• Bleach and glass or window cleaner (glass cleaners may contain ammonia);
• Bleach and chlorinated scouring powder or disinfectant;
• Drain cleaner and ammonia;
• Hydrogen peroxide and window cleaner; and
• Hydrogen peroxide and acidic cleaners with a low pH balance that are often used to remove rust and minerals from surfaces, bleach or disinfectants.

It is important to follow instructions for proper dilution of chemicals. Green cleaning chemicals, in particular, tend to be highly concentrated and it is recommended to use them with an auto-dilution system. However, cleaning agents should not be mixed with hot water, which can trigger release of potentially harmful fumes.

In a flood or water damage scenario, the janitorial closet could be a hazard zone if stored chemicals come into contact with each other. For example, toxic fumes can be released if bleach or vinegar mixes with stored automatic dishwasher liquids, toilet bowel cleaners or mildew removers.

Flood zones can present extra risks to cleaners’ health and safety so caution and proper procedures are imperative. If gas-powered equipment is being used to pump-out water inside a facility, the area must be properly ventilated. Emissions from these machines can lead to carbon monoxide poisoning.

All workers on-site should wear personal protective clothing such as electrically insulated boots, cut-resistant gloves, goggles, protective headgear, long pants and long-sleeved shirts. A tetanus shot is highly recommended in response to any skin cuts, abrasions or scrapes.

It is important to wash hands thoroughly after performing cleanup operations. Flood waters can easily become contaminated with harmful chemicals, germs, bacteria, biological hazards and/or gasoline and other petroleum products that can cause serious illness. If soap and water are not available, cleaners can use alcohol-based hand sanitizers.

Before any cleanup begins, building owners and managers must ensure it is safe to work in the area. In extreme situations, as in some of Alberta’s flood zones earlier this summer, public officials may have to inspect the property first before others can enter. Crises can turn even more tragic if ill-planned responses result in further accidents and damage.

Jennifer Meek is director of marketing for Charlotte Products/Enviro-Solutions, a manufacturer of cleaning products based in Peterborough, Ont.