Fighting fires with compressed air foam

Volume 17, Number 4, December 2012

Power transformer fire test

Compressed air foam may be the new firefighting tool when it comes to extinguishing fires in power transformers and in housing at remote locations.

After proving the technology effective in fighting fires in aircraft hangers and large liquid storage facilities (Construction Innovation, June 2005), NRC Construction researchers have shown that compressed air foam (CAF) can also protect power transformers and residential buildings in Northern communities, areas known to pose challenges for fire suppression.

A substance that resembles shaving cream, CAF is a mixture of water, foam concentrate and air, in specific proportions. When employed for fire suppression, CAF uses up to four times less water and up to six times less foam concentrate than conventional foam systems, which greatly reduces costs and environmental impacts.

Power transformers

Because of the important role they play in supplying power to a community, power transformers must have a proper fire protection system in place. Current systems employing sprinklers require large quantities of water, which can cause problems with regard to a transformer's electrical function. Clean-up can be costly as well; transformers contain hazardous materials and any run-off water from fire suppression activities has to be collected and disposed of properly.

NRC researchers carried out a series of full-scale tests to determine the fire suppression capability of a CAF system at a power transformer mock-up facility. They also conducted a full-scale test with a traditional water deluge system, to compare the fire suppression capabilities of the two technologies.

The study showed that a CAF system can protect power transformers more effectively with much less water than a traditional water deluge system. The CAF system using 1% Class A foam concentrate extinguished the test fire in about the same time as the water deluge system but used less than 8% of the water. The CAF system with 2% Class B foam concentrate was 50% faster in extinguishing time, using less than 7% of the water consumption of the water deluge system.

Residential buildings in Northern communities

Fire loss associated with housing in remote areas is particularly high because of a lack of proper fire detection and suppression systems, and the difficulty of providing fully functional fire services nearby. Installing a conventional sprinkler system in these housing units is one option. However, there is often a limited water supply and installing a larger water reservoir to provide water to a full sprinkler system is an expensive proposition.

A second option for the fire protection of these housing units is compressed air foam (CAF) technology. CAF requires far less water than sprinklers or traditional foam systems. It also has the advantage of easier clean-up as CAF produces dryer foam with uniform bubbles. Extensive water damage to contents of the building can occur after fire suppression by water.

As a result of NRC research, Canada Mortgage and Housing Corporation (CMHC) is evaluating CAF technology for the fire protection of housing units in remote areas. NRC and CMHC developed and installed a prototype CAF system in a vacant house in Yellowknife, Northwest Territories. Researchers conducted two demonstration tests: a kitchen fire scenario involving cooking oil, and a living room fire involving upholstered furniture.

The tests showed that a CAF system can provide adequate fire protection for residential housing units in a remote area with limited water supply. This is true even when activation of the CAF system was significantly delayed from the smoke and heat detector response. The delay was necessary to demonstrate that CAF could extinguish a challenging fire. The detectors would normally have activated the CAF system much earlier, an action that would provide faster extinguishment and less damage.

For more information

Contact Andrew Kim at andrew.kim@nrc-cnrc.gc.ca or 613-993-9555.