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. Wearing a respirator, even if it does not fit correctly, is better than wearing none at all. Most people cannot tell when a respirator fits properly.