Travel distance in a basement

[Rob64]

Can anyone offer advice regarding appropriate travel distances in a basement corridor? This is a sheltered housing block to which the specialised housing guide applies. The basement has a 77 metre long L shaped corridor, off of which are storage and plant rooms. It is locked and accessible only by the manager and contractors. Normal entrance is from one of two staircases serving the building. At the far end of the service corridor is an escape hatch leading to a well with a Jacobs ladder to street level, which I believe is no longer suitable as a final exit. There is currently no cross corridor separation but AFD is present and there is no sleeping risk.

If the escape hatch is discounted, this reduces directions of travel from two to one, with a full 77m travel distance. The only ventilation in the basement seems to be some air bricks. 

I’m struggling to find guidance as to  separation in these circumstances. Applying the same distances as the accomodation corridors seems inappropriate as these are intended to protect elderly residents. 

 

[AnthonyB]

Cross corridor door/partition at 30m, ladder remains as alternative exit, restricted access to suit 5/10 persons limit on ladders - there is little that can be done that is proportionate to the risk.