People have a false sense of security when wearing a faulty respirator or one that is inappropriate for the task. Respirators should not be worn when concentrations of dust are in the explosive range. A general rule is that if it's too dusty to see your hand at arm's length, the environment is dusty enough to be explosive. Another dangerous situation occurs when air-purifying respirators are used in toxic environments. Since air-purifying respirators do not provide oxygen, the air in the working environment must have at least 19.5 percent oxygen.
Death can occur in a limited oxygen environment.
Respirators that filter dust cannot protect wearers in toxic chemical environments, such as manure pits, silos, or sludge tanks. Wearing a respirator equipped with a dust filter in these conditions can be fatal. However, respirators can reduce exposure to farm dust and may prevent serious respiratory problems. People who work in agriculture develop immunities to dusty conditions over time. Wearing a respirator, even if it does not fit correctly, is better than wearing none at all.