The conditions under which work is carried out on construction sites is largely dictated by the weather, ranging from soaking wet to hot, dry and dusty. In all cases, suitable protection for the health of workers must be provided.

There are also a considerable range of substances and working techniques now in use that have created their own hazards. These include:

Cold and Wet: Cold is most damaging when associated with wet as it is then that it is very difficult to maintain normal body temperature. The effects of cold and wet can be mitigated by proper food, clothing and shelter. Shelter from the worst of the wind and wet should be provided by sheeting or screens.

Heat: Common forms of heat stress produce such problems as lassitude, headache, giddiness, fainting and muscular cramp. Danger arises when the loss of fluids from sweating is not compensated for with salt and water.

Dust and Fumes: It is essential that suitable and adequate exhaust ventilation be provided. Suitable breathing masks may also be necessary. Food should not be consumed in the area.

Sewers: Before any work is carried out in sewers, the atmosphere must be tested to ensure that it is not deficient in oxygen. Because of the gasses generated by decaying matter, smoking in sewers should be prohibited. Where the atmosphere is foul, respirators or breathing apparatus should be worn.