The relevant guidance for working out the safe capacity at your events is included in 'Fire Safety Risk assessment - Open Air Events and Venues'. Pages 68 & 69 give the relevant calculation guidance.
In essence, the maximum numbers are determined by a combination of available escape width and a risk-based escape time.
High risk = up to 5 mins, Normal = more than 5 but less than 10 mins, Low = up to 10 mins.
This is then considered alongside the appropriate flow rate for outdoor events of 109 people per metre of escape width, per minute.
The example below is specific to an outdoor event.
The width of the escape route is 5 metres wide;
5 metres @109 persons per minute per metre = 545 persons per minute
If the local risk is determined as High and escape time is deemed to be 5 mins
545 persons per minute x 5 minutes = 2,725 persons
Please note that only way to correctly determine maximum numbers at your event is for the Event Organiser to carry out an appropriate fire risk assessment themselves (if they believe themselves to have the appropriate knowledge and experience) or to arrange for a competent person to produce one on their behalf.
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