Can non-fire-rated diffusers be used in suspended ceilings in the UK?

This question has been answered by Alan Tulla, Lux Review technical editor.

This question was sent to in response to a two-minute explainer about thermoplastic diffuser fire-ratings.

If a luminaire specification does not carry any information about the fire-rating of its diffuser, it’s best to assume that it has no rating and avoid it.

The section on thermoplastic materials in the Fire Safety Part B document could be more helpful than it is currently written, but the general interpretation for the use of thermoplastic diffusers is as follows:

Ceilings of rooms and circulation spaces (but not including protected stairways) may incorporate thermoplastic lighting diffusers if ALL of the following provisions are observed:

  1. The surfaces of the void space above the suspended ceiling comply with the general provisions that apply to the space below the suspended ceiling
  2. TP(a) diffusers can be used without restriction
  3. TP(b) diffusers are restricted (see relevant two-minute explainer). 

In other words, there is no provision in the UK Building Regulations for the use of non-rated thermoplastic panels. The situation is confused, however, by the number of luminaires currently available that use non-rated thermoplastic diffusers. Lux spoke to the Lighting Industry Association, the largest trade association in Europe, who told us:

‘The LIA position is that it is not illegal to sell a panel that is neither TP(a) nor TP(b) rated as long as it is clearly stated in the installation instructions that it cannot be used if it forms part of a ceiling. Panels that form part of a ceiling (ie recessed) must be either TP(a) or TP(b) rated and be installed in accordance with the Part B regulations relating to that rating.’

So this is a case of caveat emptor (buyer beware). Unless the manufacturer’s information states clearly that the luminaire being offered contains a diffuser that complies with either a TP(a) or TP(b) rating, DO NOT BUY IT.

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