Occupancy capacity figures - reminder?

[Mar62]

I need to work out some occupancy capacity figures, which I haven't done for a while. In a large open plan floor where most is open plan office space but there are some small single person offices / meeting rooms etc and also walkways, i know you remove anything such as enclosed stairwells, toilets etc but would you remove the sqm of the small offices etc from the overall floor space? To my thinking you would, but any opinions? What about the walkways, my thinking is leave them in as they form part of the overall floor space and capacity.

[Phoenix]

General method - Take out stairs and toilets and then apply your chosen factor to the whole of the gross area that is left.  The little offices might move in the future so are ignored.  You can use 5, 6 or 10 sq m per person, depending on your guidance, or any other figure that you can justify.

Specific method - if you know how many the space is designed for then use that figure.  This approach can leave the occupants restricted when considering future alterations.

[Mar62]

Thanks Phoenix. One of those situations where people want to keep adding desks but the Fac's manager wants to draw a line. Especially as they are moving out next year anyway.

[SeaBass]

Don?t bother with the floor space factors for calculating your occupancy figures. Floor space factors aren?t important in an existing building. What you need to focus on is the capacity of the escape routes. This will enable you to work out how many people can safely exit the building under the current evacuation strategy. It may also enable you to recommend an occupancy increase, if the building is assessed and appraised under a fire engineering code, or if the protection to the escape routes is upgraded and the evacuation strategy is modified . But frankly, I?d suggest that if your that rusty on these sorts of issues, you?d be well advised to get someone more competent in this field to do the work for you, or at least get them to validate your calcs. 

[Mar62]

Hi Seabass yes will be doing those as well but client wants the occ capacity also. Good thought about verifying with someone though.

Thanks

[jayjay]

How can you ignore the floor space calculation? If the exit caluculation allows a greater number of persons than the floor caluclation then the area can be overcrowded. Both calculations should be carried out, and the one that produces the lowest number of persons is the one to be used.

[Mar62]

Hi jay jay yes agree with that. Thanks

[SeaBass]

Floor space factors are given in building design guides, ADB in this case. They are used by building designers, to work out what the probable occupancy figure will be, per square metre of floor space, for specific types of occupancy. Once the designer knows that, they can then work out what exit capacity is required for the floor area that they have, and for that specific building purpose. 
Overcrowding of an area is not a fire safety issue, so long as everyone can get out in a reasonable amount of time. Look at modern music venues where the patrons all stand shoulder to shoulder. Those facilities aren't considered to be overcrowded, so long as everyone can get out in an emergency.   

[Dinnertime Dave]

Overcrowding of an area is not a fire safety issue, so long as everyone can get out in a reasonable amount of time. Look at modern music venues where the patrons all stand shoulder to shoulder. Those facilities aren't considered to be overcrowded, so long as everyone can get out in an emergency.   

Sorry to disagree,

Whilst I acknowledge you have said as long as everyone can get out in an emergency, overcrowding can lead to Progressive crowd collapse at the time everyone is trying to leave, this will slow down any evacuation and cause injury.

I was taught during event safety courses to get up high and observe the crowd. If looking down you can see heads and shoulders generally less chance of PCC. If you can only see only head there is a problem.

More here - http://www.gkstill.com/Support/Links/CV/Modelling/CrowdCollapse.html

[Tom Sutton]

Check out http://www.crisis-response.com/forum/?topic=4985.0 may be worth a read?

[Mar62]

Thanks all, thanks Tom.