All internal fire doors must be certified. Check for a label on the top or side of one of the doors to ensure this. You should also check that the gaps around the sides and top of the doors are less than 4mm when closed. You should just be able to fit a £1 coin in the gap (as a way to determine whether the gap is too big). All seals around the fire doors should be in good condition, with no damage. If they are damaged, they will need repair, as the performance of the doors could be compromised as a result. A final check is to ensure that the doors close properly. You can do this by opening the doors halfway and then letting them go, to see if they close by themselves. If they stick onto the frame and do not close effectively by themselves, they will need further examination and repair. If you require internal fire door installation, maintenance or repairs, RES can carry out a comprehensive service to meet your requirements. We cover the South of England including the counties of Berkshire, Middlesex, Surrey, Oxfordshire, Hampshire, Buckinghamshire, Hertfordshire, Essex, Kent including London, Aldershot, Basingstoke, Beaconsfield, Bracknell, Egham, Farnham, Guildford, Henley on Thames, High Wycombe, Maidenhead, Marlow, Newbury, Oxford, Reading, Slough, St Albans, Staines, Swindon, Watford, Windsor, Woking, Wokingham.