I am trying to write a workable procedure around Hot work for one of our manufacturing facilites. Hot work would not be a common activity at this particular site. 

I am being challenged (and its a good challenge) over the duration of the fire watch period. I've looked at guidance from FM global Allianz etc.. and some suggest 120 mins.

The site is not a 24/7 operation (9-5) and so we would be asking people to stop all hotwork activities at 15:00.

Is it possible that fire watch time period to be determined by a risk assessment? A person grinding a peice of metal in a room with no combustible material around would not require a 120 min fire watch, but on the otherhand welding pipework in an area where combustibles can't be moved would require more vigilance etc..

How do other people manage this

Check with your own insurer, if you go by FM Global then you need to be aware that they set a really high bar which is not based on risk assessment as we know it in the UK.  Most insurers ask for hot work to cease an hour before the site shuts down for the day and if covered by a hot work permit with protection / removal of combustibles the fire watch is for one hour.  BUT you have to be able to prove that you have robust procedures for control of hot work and prevention of ignition.

I've seen 30 minutes and 1 hour fire watch duration in hot works procedures in the past.  2 hours does sound onerous.

FM Global were the insurers of this risk in my last business.  They specified 1hr continuous watch and a further 3hrs of periodic (no more than 30min intervals) after that.  The stipulation was applied globaly even in territories that had not seen an insurable fire event.

Most of this requirement built up over time.  Initially it was 30 mins continuous fire watch, but there was a claim that was based on a fire starting after this period (in reality its entirely likely the fire watch didn't actually last 30 mins but no one was going to admit that as it would invalidate the claim).

Then it was 1hr continuous fire watch, but there was a claim that was based on a fire starting after this period (in reality its entirely likely the fire watch didn't actually last 1hr but no one was going to admit that as it would invalidate the claim).

Then it went to the 1hr plus monitoring.

Whilst its hard to accept, the insurers will make stipulations ENTRELY to protect their business from risk.  They are very rarely swayed by your risk assessment or limitations of working practices.  There are two choices (with some grey area in between).  Either comply with their stipulations or work with our own acceptance of risk or implemetation of safety theory and accept you risk not being insured.

Over the years I have come to the conclusion it is rarely worthwhile trying to reason with insurers requirements as both parties are looking at the risk from diffeent standpoints and you probably need them far more than they need you.