Hydrogen sulphide gas present in tanneries and effluent treatment plants has proven fatal to workers exposed to it many times. It is therefore necessary that the owners and managers of tanneries and effluent treatment plants are fully aware of the dangers posed by this poisonous gas and take all preventive and precautionary measures to protect the workforce from exposure to this gas. In the event of accidental exposure of a worker, they should know how to deal with the situation. The lessons that follow are to help tanners, tannery managers and operators to acquaint themselves with the basic principles How to deal with hydrogen sulphide gas. The on-line course developed by UNIDO including test provides an opportunity for the proper training within tanneries related to danger associated with hydrogen sulphide gas. After finishing the test with minimum score 80%, participants will receive the certificate and will be able to download it.