Harmful substances can enter the body in three ways : -
a) Through normal breathing
b) By being absorbed through the skin eg: paint solvents can be absorbed through the skin.
c) By being swallowed
Harmful substances can pass from your hands to your food and then to your stomach.
Of these three modes of entry, breathing of harmful contaminants is the most common.
Generally, there are 5 types of contaminants in the workplace that are potential respiratory hazards: dust, mist, fumes, gases and vapours.