Focus on cold storage: Blow hot and cold

The notion that fire could be an issue for cold stores feels counter intuitive, but cold stores particularly those that form part of larger food production facilities built up quite a reputation as a fire risk at one time, sending insurance premiums rocketing skyward. Regulators and insurers have been piling on the pressure to improve the situation and this has paid off over the past five years. Nevertheless, there remain risks associated with the insulation in many older facilities, while the risks associated with refrigeration plant are on the rise.

Composite panels are widely used to provide the insulation for chilled storage. These panels contain a central insulating core sandwiched between layers of facing material such as steel. In the past, the insulating materials commonly used in these panels were highly combustible, such as expanded polystyrene or polyurethane. New panels are much safer, with fire-resistant core materials of mineral fibres or treated polyurethane or polyisocyanurate (PIR). "A combination of treatments and the steel sheet around the core means that PIR cores these days can offer two-hour fire integrity," says Carl Moon, senior estimator for cold room contractor ISD.

The problem remains, however, that many existing sites still use the old, more combustible panels, and insurers are reluctant to offer cover in these cases. "They may not cause fires in the first place but panels tend to contribute to things being a total loss," says Dr James Glockling, technical director of the Fire Protection Association (FPA). "A lot of companies have spent a lot on replacement regimes taking out polystyrene, but panels are still at the heart of some problems. Thankfully insurers are taking a practical view and asking for replacement around critical areas."

Human life at risk​

Older combustible panels not only pose a risk to buildings, but they also put fire fighters in more danger, leading to some brigades refusing to enter buildings where they are used. The trouble is that it may not be obvious when officers arrive at the scene of a fire which type of panel they're dealing with.

The International Association for Cold Storage Construction (IACSC) therefore promotes a labelling scheme to tell fire fighters what's lurking inside panels. It also tells them whether the panels are certified as fire stable by the Loss Prevention Certification Board, which is part of Building Research Establishment. Certified panels should not delaminate as they heat up in a fire and no flaming droplets should be released by the core materials. This is especially important in ceiling panels.

Insurance drives standards​

Any feature such as a doorway, vent or duct that compromises the skin of composite panels can impact on fire resistance if the installation is not carried out properly. This makes it highly advisable to opt for reputable contractors that work to accepted construction standards, such as LPS 1500. "It's mainly insurance rather than regulation that's driving this, but it's important to keep driving up standards so that every building is constructed properly," says Moon.

If anything, the use of composite panels is becoming more widespread. They're lightweight and convenient to build with, so where contractors may have built plant rooms associated with a cold store from concrete/aircrete blocks in the past, they're often specifying panels in today's projects, according to Moon. He also says that a greater risk of ignition can occur here. "The cold store itself is low risk for fire, but it's the surrounding plant rooms and offices that pose a risk."

"The actual risk posed by a cold store when it is being put to the use it should be put to is minimal. The real issue is the rest of the factory," agrees Chris Sturman, chief executive of the Food Storage and Distribution Federation. Hot equipment in food factories, such as ovens and fryers, presents a particular risk. It's vital to safeguard the integrity of cold stores by designing facilities to keep insulating panels at a safe distance from such potential hot spots.

While it's insurers rather than legislators that are driving a lot of the risk reduction initiatives, the changing regulatory regime has also had an impact. Approved Document Part B (Fire Safety) of the Buildings Regulations governs the design and construction of buildings, while the responsibilities on owners to operate a building safely and plan an effective response in the event of a fire are laid out in the Regulatory Reform (Fire Safety) Order 2005 (FSO). The arrival of the FSO in particular marked a pronounced shift away from relying on inspections by the fire services towards making it the responsibility of building owners to carry out comprehensive risk assessments and act on them.

There's also plenty of guidance available on best practice. The FPA produces a raft of design guides from essential principles covering all buildings to specific documents for food factories and cold stores. In addition, the IACSC published the second edition of its guide for the Design, construction, specification and fire management of insulated envelopes for temperature controlled environments in 2008.

Other fire risks ​

Construction materials are not the only fire risk associated with cold stores. Any temperature controlled environment needs a refrigeration plant and many of these are about to pose more of a danger from fire than they have done in the past, thanks to legislation designed to protect the wider environment.

The Ozone Regulation came into force across Europe in 2000 and it has already banned the use of ozone-depleting hydrochlorofluorocarbon (HCFC) refrigerants such as R22 in new systems. Even so, R22 remains common in existing systems used by food and drink manufacturers, but that's about to change. The Regulation bans the use of virgin R22 as a 'top-up' fluid for maintenance from 2010 and a ban on the use of recycled R22 will follow by 2015. All remaining users of R22 and other HCFC systems therefore need to consider their options.

Many HCFC alternatives are based on hydrofluorocarbon (HFC) refrigerants. The downside of these alternatives is that they fall foul of the F-Gas Regulation, which came into force in 2006. F-Gas places extra obligations on the owners of HFC-based refrigeration plants because these compounds are potent greenhouse gases.

Anyone looking to avoid HFCs is left with refrigerants such as ammonia, hydrocarbons or carbon dioxide, all of which require the replacement of existing plant. In the case of both ammonia and hydrocarbons they also create a fresh fire risk.

A notorious incident took place in 2008 at Tamahere, New Zealand, and showed what can happen when things go wrong. A fire started when leaking propane gas refrigerant was ignited by electricity and exploded. Eight fire fighters who were on site to investigate a smoke alarm were caught in the blast. Six were seriously injured and one man died.

Issues with ammonia​

"Ammonia is already the refrigerant of choice for many of our members," says Sturman. "There is an issue of flammability so there need to be certified systems in place to detect any leaks and evacuate systems to prevent ammonia being present at a concentration to cause an explosion. There's also an issue with engineers who are working on these systems. There have been some incidents where people have been overcome by ammonia in confined spaces."

If, or when, a cold store does catch fire, the harsh environment presents a special challenge for fire detection and suppression systems, according to Alan Hughes, director of Bristol-based distributor Fire Suppression. The answer for early detection is to have aspirating systems that draw in air and carry it to detectors positioned outside the cold area.

The need for regular wash downs is an added problem for food companies. "There can be problems with water ingress in some aspirating systems," says Hughes.

"The very low temperatures in cold stores can also cause condensation that creates a build-up of ice, which means that sampling the air is not so easy." He advises cold store operators to opt for aspirating detection systems that have been specially designed for tough conditions, such as the Vesda system favoured by Fire Suppression.

Sprinkler systems also have to be specially designed for sub-zero conditions, but the bigger issue here is that most British facilities are not required by law to use them, according to Glockling: "We are so far out of kilter with the rest of Europe. You need to be in a space two and a half times the size of Wembley to have mandatory sprinklers."

British premises must be 20,000m2 in size before they are required to fit sprinklers, while Germany's limit is 1,800m2. Glockling points out that business losses from fires in the UK for the year 2008 were £865M, compared with £400M in Germany.

He also acknowledges that installing sprinklers is an expensive process and that companies are wary of the potential for them to cause widespread water damage: "Companies may well use sprinklers to protect particular items of equipment, such as a fryer, without a wider system in place. But if the local system fails the result could be that you lose the entire building. Sprinklers may cause damage but at the end of the day you'll still have a building."