Hi,

Can you please tell me what the recommended height that a fire evacuation sign should be placed ? (if it exists)

I notice that many are placed at head height - but I would have thought that lower to the ground would be better because in a fire the smoke rises and therefore people evacuating could well be down at floor level - so it would seem better to place them nearer the ground.
Any advice would be appreciated

If they are "nearer to the ground" they would be more likely to be damaged.

Also would it not "be the norm" that everyone gets out before the smoke reduces visibility, and the natural reaction of Joe public would be to run, so again, a sign low down would be of no use.

You will find the following in BS 4499 part 4 2013,

Mounting height

Escape route signs should be sited conspicuously within the normal field of vision.

To assist evacuees with the prediction of the location of successive signs, the Following principles should be applied:

a. Signs above doors or open spaces should be mounted between 2 m and 2.5 m from floor level, measured to the base of the sign and be sited as close to the centre line of the escape routes practicable;

NOTE 1 This mounting height is intended to ensure that signs can be readily seen, e.g. over the heads of people.

b. Signs sited on walls should be mounted between 1.7 m and 2 m, from floor level measured to the base of the sign;

NOTE 2 This mounting height is intended to ensure the signs are within immediate field of vision

c. Mounting heights greater than 2.5m may be used, e.g.in large open spaces or for operational reasons, but such signs should be both conspicuous and identifiable therefore larger signs might be necessary;

d. Signs should be sited at the same height throughout the escape route, so far as is reasonably practicable.

As green-foam has said everyone should be out before the smoke reduces visibility and if this is not the case the FR assessor has done a poor job. If you are interested in low level signing check out BS ISO 16069 2004. Safety Way Guidance Systems.