Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Fluid category
  • Title : Humidifiers
  • Clause Reference : Schedule 2 paragraph 15 & G15.3
  • Reference Number : B40
  • Decision Date : May 2010

Those Humidifiers which introduce water either as steam or by spraying it into an air stream are regarded as a fluid category 2 risk. Where these units are supplied with a drain to waste a fluid category five device such as an air break to drain is required at the waste connection.

Humidifiers that pre-treat water using reverse osmosis units that employ larger scale industrial processes which use chemical additives, for example to clean the reverse osmosis membrane are, depending upon the outcome of a risk assessment, either a fluid category 4 or 5 risk.