a protected species?

A lighting cover with a one hour rating to Part 23 may only be able to protect a timber decked / joisted floor for 15 to 25 minutes because of the positive pressure used in a Part 21 test. This is far too short to provide the 90% cover required for a loaded lightweight joisted floor, if it is to achieve the one hour separation rating.

Some down lighters get very hot in use with temperatures at the rear of the fitting exceeding 200ºC. Fire covers can protect the fitting from being in contact with flammable or insulating materials present in the void and being manufactured from intumescent fibre material have good acoustic properties.

Fire covers however, can cause overheating of the down lighter with a resultant significant reduction in lamp life and if they are of the vented style to prevent this overheating, they then lose their acoustic performance.

The simplest, most economical and safest (the protection having been properly installed) solution is to select down lighters that have protection built into them, have been tested in representative ceiling / floor structures to BS476 Parts 21 or 22, have had a full acoustic test and are capable of being in contact with materials in the void without creating a fire hazard or over heating problems.

Such a range has been developed and patented by FL Patents Limited and is being manufactured under licence and marketed by Electro-Technik Limited. This low voltage down lighter range is available in fire ratings up to 1.5 Hours , meets all the above test criteria, is extremely simple to install from below and is approved by LANTAC and Zurich Building Guarantees.

For more details please telephone 01527 595349 or visit www.electro-technik.com

Down lighters provide a very attractive modern and efficient form of lighting. Their clean lines suit many modern interior designs, they can illuminate or concentrate light into difficult areas, increase the feeling of space and mix well with other lighting elements to create a very pleasant ambience.

However, if during their installation, no consideration is given to fire and location protection, then a reduction in the fire rating of the structure will occur resulting in non compliance of Building Regulations. Also, in some situations the down lighters themselves can introduce other fire hazards.

Building Regulations, Approved Document B ( Fire ) states "If a fire separating element is to be effective, then every joint, or imperfection of fit, or opening to allow services to pass through the element, should be adequately protected by sealing or fire-stopping so that the fire resistance of the element is not impaired"

The technical standards of Scotland and those of Northern Ireland say the same.

Structural floors are highly dependent upon the fire protection provided by the ceiling lining for their fire resistance period. This applies to floors constructed with joists of timber, steel or a combination of timber and steel.

he perforation of this ceiling membrane, to fit recessed down lighters, will cause a down grade in the fire rating of the structure. This reduction can be considerable where modern I beam or metal lattice joists are used. These styles of joists have many constructional advantages plus the very economical use of wood. As a result, they do not have the sacrificial timber that traditionally provide the protective charcoal which allows timber structures to achieve their fire resistance. They may therefore be unable to withstand fire exposure for more than 5 minutes.

It is therefore essential that consideration must be giving to maintaining the fire resistance of that protective ceiling lining and ensuring that the down lighters fitted, are so protected, that they reinstate the properties of the ceiling material that has been removed.

It is unfortunately very often considered that the perforation of the ceiling will only result in a loss of integrity and that, if the floor boarding is of reasonable thickness and well jointed, this will not result in a failure of the fire resistance because the floor will resist burn through.

This is particularly so in domestic housing where the rating is only 30 minute load bearing capacity. However, ceiling perforation puts this load bearing capacity at risk and if an unprotected installation of down lighters fails to keep fire out of the cavity for 20 minutes, then a premature collapse could occur.

This is a risk that should not be taken.

The compliance to building regulations of fire rated structures is carried out on a case by case basis but sometimes it is difficult to judge, visually, whether protection or protected types have been installed and whether this been done correctly. Better then to remove the doubt and make down lighter protection the acceptable standard.

Also, as now being highlighted by Building Regulations E, this ceiling membrane has also a critical role to play in maintaining the Acoustic Rating of the structure.

Again, perforation of the ceiling will result in a down grade of its acoustic properties and any down lighter fitted or its protection must be capable of restoring that acoustic rating.

For domestic housing applications, protection is provided by the use of lighting covers or the fitting of down lighters where the fire and acoustic protection is built into the light unit itself.

Care needs to be taken in the selection of a lighting cover to ensure that it is right for the application. Some covers are only tested to BS 476 Part 23. This is a test for light fittings used in association with commercial suspended ceilings designed solely to protect steel beams in lieu of applying protection. It is carried out at zero pressure differential at ceiling level and therefore has no function in respect of floor tests to BS 476 Part 21 or 22.