Flexible polyurethane (PU) foam – reducing fire risks
Manufacturing PU foam is an exothermic reaction so the foaming process needs to be carefully controlled to prevent foam reaching excessive temperatures. The highest temperatures will normally be in the centre of a block.
When manufacturing PU foam you should:
- know the degradation or charring temperature of the foam
- periodically measure the temperatures within large blocks
- have written procedures of what to do if a block overheats eg transfer to a safe place outside the building
- plan workflow so minimal amounts of PU is kept in process areas
- remove finished goods as soon as possible to the store or despatch area
- where practicable keep bulk stores above workrooms in multi-storey factories with a downward workflow
- carryout processes involving large-scale handling of easily ignitable substances (eg highly-flammable liquids or crumb) in a fire-resisting enclosure on the top floor
- monitor and manage workroom stock levels (including raw materials and part/processed materials)
- manage stock levels so they are generally not more than 10% the total area
- where necessary put additional safeguards in place when stock levels exceed 10% the total area eg in conversion processes where products are almost entirely PU foam
- minimise times when stock levels are over 10% the total area
- may need to check the quality of chemicals used in foaming
Flexible PU foam waiting processing and shaped materials eg finished cushions should be arranged in stable stacks using pallets or racks where necessary. Rolls of laminated material should be kept in racks. Upholstered furniture may be kept in single units, racks or stable stacks as appropriate.
All materials should be kept in well-defined areas separated by marked gangways and following the guidance on storage.PU foam and work-in-hand incorporating PU foam should be stacked in workrooms following the guidance on positioning stock in storerooms. Materials in workrooms should not be stacked within 1m of any part of a fire exit.
It Is not recommended to keep PU foam or finished products against internal glazing or directly under any elevated working area. Elevated working platforms and galleries are not recommended in PU foam workrooms. Where these exist, PU foam should be kept as far as possible away from them and adequate fire protection and means of escape must be provided.