The TTL tests In 1996, the DoE and TRADA commissioned TRADA Technology Limited (TTL), a member of the TTL Chiltern group of companies, to test the effect of recessed downlighters (with no boxing in or fire hoods) on the fire resistance of plasterboard ceilings with conventional rectangular joists. TTL has been involved in fire research and testing for many years and is the UK’s leading authority on the fire protection of timber. During 1994/95, TTL carried out the tests. The results of the tests were published in the July 1996 edition of Building Control magazine. These results were, perhaps, surprising in that they confirmed that downlighters, even without being boxed in and with no fire hoods, in plasterboard ceilings have little significant effect on fire resistance ratings up to 30 minutes. It must be inferred from these tests therefore, that, at least with plasterboard ceilings with conventional rectangular joists, it is not necessary to ‘box in’ luminaries or to use fire hoods for the purpose of restoring the fire resistance capability of ceilings which are not of fire compartment construction.