Major Hazard Installation(MHI)

What is MHI

MHI is the short form of “Major Hazard Installation”, in the context of Singapore’s WSH(MHI) Regulation.

MHIs refer to fixed installations, including Petroleum refining and manufacturing facilities, chemical processing plants and facilities where large quantities of toxic and flammable substances are stored and/or used.

MHI classification

A workplace will be classified  as an MHI under the WSH(MHI) Regulations, if it meets both of below two conditions:

  1. its nature of work activities, and
  2. its inventory levels of dangerous substances (present or likely to be present) meeting or exceeding threshold quantities.

For condition 1, the works activities involve processing, manufacturing or having bulk storage by way of trade or for the purpose of gain of any dangerous substances specified in the First Schedule of WSH(MHI) Regulation.

Condition 2, on the quantity of dangerous substances,will be satisfied  if at least one of the below two criteria is met:

2.1 Quantity of the individual dangerous substance present or is likely be present equals or exceeds the prescribed threshold quantities; or

2.2 aggregation of the ratios of dangerous substances for one or more hazard classes(i.e. Physical, Health or other hazards) equals to or exceeds 1.