When a Health and Safety and Risk Assessment Officer working for a major regional police force contacted IFSA for guidance in respect of the influence of the overpainting of intumescent seals, IFSA were only too pleased to help the officer in question ‘with his enquiries’. An extract from the Association’s reply is repeated below because it is a subject that frequently arises.
‘The issue of overpainting was addressed a long time ago when there was a suspicion that two-pack polyurethane varnishes could reduce the effectiveness of intumescent and also when paint was much more likely to be solvent based, rather than water based. With a water based system the only combustible material would be the organic residue that gives the colouration or some of the physical properties, such as flexibility. It is difficult to envisage when the build-up of such restricted combustible material could seriously compromise the fire resistance of the door. It has for a long time been possible to conceal one of the pressure forming intumescent materials beneath a timber lipping without impairing its ability to seal the door edge, albeit indirectly. I think that perhaps this leads us to the answer to the question. It is IFSA’s belief that any seal which is based upon sodium silicate (Palusol), or a compound incorporating intercalated graphite which produce pressure when activating, should not suffer a critical loss of performance when overpainted, almost without restriction. Overpainting a low pressure seal, such as polyammonium or monammonium phosphate should be treated with caution, and not more than 5 coats should be allowed to build-up, albeit one recognises the difficulty of establishing when that is reached. Any seal within a ‘plastic’ extrusion will invariably be sodium silicate, or graphite, whilst strips not in a plastic holder may be assumed to be phosphate based. Finally, IFSA would like to state that our guidance on overpainting is strictly related to the performance of the intumescent seals. Overpainting of smoke seals is likely to have much more serious performance implications.’
The enquiry did, however, give the Association the opportunity to recommend its two electronic Technical Communiqués Nos. 1 & 2. These are specifically aimed at the Risk Assessment community, identifying the implications that inadequate sealing may have on life safety.
If you have not yet downloaded your copy, go to www.ifsa.org.uk and do so without delay.
