The Health and Safety (Safety Signs & Signals) Regulations 1996 require employers to mark visible pipes in the workplace which contain or transport dangerous substances.
BS1710: 1984 Identification of Pipelines and Services, specifies the colours to be used for the identification of pipes containing or transporting dangerous substances, inlcuding conduits for electrical and ventilation ducting.
Pipleline identification markers are manufactured from high quality self adhesive vinyl and are supplied in packs of 5. Each marker is 300x40mm and has a twin flow direction system so you can simply remove the direction which is not required.