I have just surveyed a three storey property converted into 3 flats. There are gas meters and pipework in the single protected staircase. My instinct is to recommend enclosure with 30 mins FR. However, the building regulations states that gas service and installation pipes or associated meters can be incorporated within a protected stairway if the gas installation is in accordance with the requirements for installation and connection set out in the Pipelines Safety Regulations 1996, SI 1996 No 825 and the Gas Safety (Installation and Use) Regulations 1998 SI 1998 No 2451. Does enclosing it break the requirements for ventilation? Can anyone offer advice on this? Thanks in advance.

This is the ACOP to the regulations which should help you assess the set up, usually an enclosure is vented if used.

http://www.hse.gov.uk/pUbns/priced/l56.pdf

You may want to consider the Lacors Guide:

https://www.rla.org.uk/docs/LACORSFSguideApril62009.PDF

See Page 18  Para - 15.5

Gas or electric meters and/or distribution boards should ideally not be sited in escape routes. However, it should be possible to relax this providing any gas meter is installed in accordance with the gas safety regulations and any electric meter is installed and sited in accordance with current IEE regulations. It is considered best practice to enclose such equipment in fire-resisting construction.