My experience with sourcing the spec for metal fires was borne through a service of a firm who dealt with metal ingots. Melted them down in one of three foundries and processed the results to forward on to their clients. A fire erupted in a warehouse in which were 20 plus pallets, single storey, of mixed metal ingots. Covered with 2 x 9Kg ABC powder.
Throughout site were ABC powder, water and AFF Foam. The foundries themselve were covered with the same.
The Brigade came through, unwound their hoses but before the yound lad blew himself up it was suggested that perhaps he didn't try to put out the fire with water. Neither he nor his collegues were too chuffed when a mere extinguisher engineer tried to tell him his job but tough ****. We all survived to have a brew.
I spent a long time pouring through the firms COSHH sheets and trying to find BS or EN spec on metal fires from manufacturers, suppliers, powder manufacturers etc. To no avail, I found nothing to specifiy Standards for metal fires.
Then someone pointed out the obvious: metal comes in all shapes, sizes, types, storage, etc so to standardise an extinguishant or create a spec. is impossible. Each case is unique.
All I do now when asked to specify types and sizes of extinguishers for metal fires is check out the COSHH and then the type of Class D powder required to cope with a particular metal, as has already been written in earier posts, there are many manufacturers with specific types of Class D powder for specific metals.
As with any new kit, training is vital if the kit is to be used. As for sizes, there are 9Kg,12Kg and then wheeled mobile units. Do as much homework as you can before you purchase fire cover and ensure it is the correct medium for the specific risk. We are legally obliged to ensure the client has the correct kit for the risk presented in every premises and they fully expect that. But the customer is also obliged to ensure staff are trained in what to do in the event of a fire.
In the above case all problems were covered with Amerex 9Kg, staff training and upgraded signage warning in restrictive use of water.