Aerosol Cage

[Andy W]

Good morning all.

We currently have an enclosed aerosol store but due to increased stock this has become too small. The aerosols are 200ml & 50ml and its only the propellant that is flammable.

We have looked at a section of the warehouse where pallet racking is against an internal wall- and we intent to have mesh around the section that will hold the aerosols (25mm x 25mm).

The question has been raised as to the requirement of a roof to the cage- we have differing opinions on this.

Option 1- put a mesh roof on. The insurance company want this.

Option 2- mesh right to the roof- this would be the cheaper option and if favoured by the Director. In the caged area there are 3 sky lights- exploding aerosols could easily break through these. However, they would have to clear a section of warehouse of about 50,000 sq ft before they came into contact with civilisation. We could mesh the sky lights quite easily. The roof is metal on the outside with plasterbourd panels on the inside.

We are planning to challenge the insurance company with regard to the fully enclosed mesh.

Do any of the learned people on here have any experience with this type of situation? Do we have grounds to cahallenge?

My feelings are that we do- I may be wrong.


Does anyone know the rough travel distance of an exploding aerosol?

Thanks in advance

Andy W

[nearlythere]

Why not fully enclose to FR standard and vent to outside? Should your FS stategy not be to protect the aerosols from a fire in the building?

[Andy W]

The area will be fully enclosed- mesh on one side of the racking, a brick wall on the other side, and mesh on the front (self closing door for FLT entry) and rear (break glass fire escape door) and the roof to fully enclose. Our insurers have stated that we should mesh the top and not use the roof to enclose.

Its an added cost that is felt is not required.

Andy

[John Webb]

Andy - an exploding aerosol can travel up to 200m depending on circumstances (how heated, degree of confinement....). I suspect the insurers may be asking for a mesh over the top to prevent aerosols bouncing off the roof and into the rest of the warehouse or even breaking through the roof and starting a fire on the roof?

[Andy W]

Cheers.

The roof is metal with plastic skylights. Any aerosol that becomes a projectile will not be able to bounce off of the roof into different parts of the warehouse, as the mesh will be up to the roof on three sides and a brick wall is the fourth side. From the position of the proposed store if an aerosol did go through a skylight it would not reach civilisation, even at a 200m distance. We could mesh the exposed skylights, as there is only three of them.

Andy

[kurnal]

Is the warehouse sprinklered?

[Andy W]

We have in rack sprinklers. A fire proof room for flammable liquids.

The products we store are mostly plastic, in cardboard packaging on wooden pallets.

One of the reasons that the insurance company is a bit on edge is because we (prior to me working here!) burned the last warehouse to the ground. Total loss of stock, no sprinklers in that one.

Andy

[Dinnertime Dave]

I have 3 of these aerosol storage areas in my area two of these use cages but neither have a cage at the top. The other is fully enclosed in 2 hr fire resistance (best practice according to HSE) but again not at roof level. All are sprinklered, one because of extended travel distances using BS9999. one because of compartment sizes. The other is an American company that likes sprinklers.

check out HSG51 and from memory TB219? in BS EN 12845 for some good information on the risks. flaming caps is a lesser considered risk.

Also, if you have more than 50 tonnes of of flammable content you will fall under COMAH Regs (lower tier). I have always found the HSE really approachable on this subject.   

[kurnal]

The LPCB rules for sprinkler protected buildings have quite a lot to say about aerosols.
General guidance is covered in TB 216

“Aerosol containers present a special hazard within sprinkler protected buildings. The flammability of aerosols varies, depending on their contents, but all types of pressurised aerosol container could be responsible for the transmission of fire within a storage by burning projectiles. Storages containing aerosols should be treated as a special case and the requirements of Technical Bulletin TB216: Sprinkler protection of aerosols, should be complied with. The fire insurer should be consulted concerning the standard of protection required.

An aerosol dispenser is defined as ‘a non-reusable container made of metal, glass or plastic containing a gas compressed, liquefied or dissolved under pressure, with or without a liquid, paste or powder, and fitted with a release device allowing the contents to be expelled as solid or liquid particles in suspension in a gas, as a foam, paste or powder, or in a liquid state.’ For the purpose of this document the term ‘aerosol’ will refer to an aerosol dispenser and its contents. Aerosols having a container made of metal shall have a capacity of 1000ml or less and if made of glass or plastic 220ml or less. In Europe, aerosols should be identified and marked as flammable if the contents include more than 45% by weight, or more than 250g of flammable components. This differs from the US classification which designates three levels of classification,
Level 3 and some of the Level 2 products being equivalent to the European flammable aerosol classification.
Mechanical damage of a pallet or box containing aerosol products, leading to a release of contents, may result in a fire if there is an ignition source present. Once aerosols become involved in a fire the containers are likely to fail due to the effects of increasing external temperature and the resulting increasing internal pressure or due to degradation of the valve closure. Any container failure is likely to result in the container or adjacent containers being expelled forcibly from the fire site. If the aerosol containers are not restrained, container travel distances of 30m and more.”

Specific guidance on aerosol cages and sprinklers is contained in TB216. I think you are going to need a top on the cage at the very least to the same standard of mesh as the walls. And probably sprinkler heads in the cage depending on system type , specification and ceiling height etc.

The British Aerosol Manufacturers Association also publish a guidance document but to be honest having bought it I wouldnt recommend it to anyone else.
If you email me with more details of your sprinkler systems I will forward you some more specific advice.

[Dinnertime Dave]

It appears my memory isn`t that good then - not 219

With regards to the mesh roof perhaps playing devils advocate here - what does it add? The roof will stop flying aerosols and caps in the same way as the mesh cage. Neither is fire resistant. 

[kurnal]

If reliance is placed on ceiling sprinkers Dave then you are probably right but depending on sprinkler spec, size of store, height of ceiling and mode of storage in rack sprinklers or cage top sprinklers may be required. ESFR sprinklers can often cope without in rack sprinklers but maximum ceiling height is still limited. so if in rack or cage top sprinklers are required then the exploding aerosols must be contained.

[kurnal]

In simple terms it seems to me that your insurer is asking for something entirely reasonable and appropriate. Sprinkler systems are designed around an expectation that if you have a fire, based on your contents and layout the sprinklers will control and suppress that fire. It will not grow to affect more than a small area. The design considers how quickly the fire will grow horizontally and vertically and the number of sprinkler heads that are expected to operate before the fire is contained.

The water supply requirement is then calculated based on that number of heads operating- this includes size of pipework to support the flow, size of pump, size of tank. The worst case scenario is if the fire grows beyond the design size – then the water supply will be unable to support the number of sprinkler heads that operate, the flow from each head becomes a dribble and the fire continues then to grow unchecked.   

As you have in  rack sprinklers the system typically expects any three heads on any three rows to operate- yours may be a little different but 9 heads is typical for the design of an in rack system. That’s why the insurer wants a roof on the cage because it will help to contain the aerosols, as far as possible, within the immediate area of the fire. The further they fly vertically the wider the area they can affect horizontally, setting off more heads than the water supply can support.

The sprinkler system needs to use all its water to contain surround and drown the fire beneath it. It can only cope with one fire at a time. The cage roof will help contain any flying aerosols to enable this to happen.