Nick As far as I am aware there is no legislative control for the cleaning of filters in ceiling cassettes or wall mounted VRV/VRF type units. Refrigerant yes, loss of gas yes but cleaning I am not aware of (from a prescriptive stance). Generally the filters blades and central intake are all that require cleaning. It takes just a few moments to run a vacuum cleaner nozzle over it, and perhaps this could be undertaken by the cleaning company (if you have one), saves staff having to get mucky, saves you training them, and best of all you have eliminated work at height:-) I can't suggest frequency rates because I don't know how dusty you are there - and how many employees you have. Open doors, dirty carpets, but above all else it will be skin particulates that create the most clogging. When you next get changed and the sun is shining through the window watch just how much dust (skin) you make when you get undressed. CFT

Finally, can anyone tell me where I can find a full copy of the legislation and ACOPs?

Nick you could start with Approved Document F, then from there and HSG 202 (which seems unavailable in the HSE website) . Both documents point you towards the CIBSE document TM26:2000 Hygiene Ventilation of Office Ventilation Ductwork, which should give you some guidance. Info in above post is correct, have to make it suitable and sufficient in order to not cause any problems for workers, no dust build-up etc and is related to risk assessment of the dust etc being created and how it needs to be removed. Martin

Hi all Thank you very much - your help is really appreciated. Thanks where itis due - I remember when I used to use these forums before, that there were a lot of people that would pop in and ask a question, then never be heard of again (and never say thanks). Nick.