This question has been answered by Alan Tulla, Lux Review technical editor.
This question was sent to firstname.lastname@example.org 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:
- The surfaces of the void space above the suspended ceiling comply with the general provisions that apply to the space below the suspended ceiling
- TP(a) diffusers can be used without restriction
- 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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