What are the ventilation requirements when working with hazardous substances, what do the regulations require etc

Ventilation of the building – you need good general ventilation, which normally means five to 10 air-changes per hour - talk to a heating and ventilation engineer.

Ventilation of a process, usually called local exhaust ventilation (LEV) means extracting any gas, vapour, fume, mist or gas from a source of airborne contaminant. The rate of extraction depends on the size of the source. The shape of the hood that collects the contaminant cloud depends on the speed and direction of the contaminant cloud. You need to talk to a competent person. See:

	[INDG 408, Clearing the air, A simple guide to buying and using LEV](http://www.hse.gov.uk/pubns/indg408.htm) and,

	[INDG 409, Time to clear the air!, A workers pocket guide to LEV](http://www.hse.gov.uk/pubns/indg409.htm)

See HSE's [local exhaust ventilation website](http://www.hse.gov.uk/lev/index.htm)

Don't forget that ventilation has little effect on exposure of, or through, the skin