Michel Wizenburg discusses BS9991
Similar to BS9999, due care must begiven when using this document as it is not possible to pick and choose. Therefore,if BS9991 is implemented in a design, it must be donefully, which could affect other areas of the building that were previouslyacceptable as some of the design requirements in BS9991 are more onerous incomparison with ADB (e.g. 1.0m┬▓ passive vent required from basement lobbies ofsmall single staircase).
Nevertheless, there are benefits inusing BS9991 and one example is the allowance of doubling the travel distancesover the recommendations from ADB if the building is sprinklered. This documentthen gives the developers / designers with flexibility over their design ofresidential buildings in a similar way that BS9999 provides an alternative wayto design a commercial building.
The one piece of advice I would giveis to ensure that if BS9991 is going to be implemented in the building design,this should be agreed with the Approving Authorities before proceeding.
Michel Wizenberg, Managing Director, FDS Consult