Following the devastating explosion at the Buncefield oil storage depot in Hertfordshire in 2005, there was a shake-up of how agencies respond to major incidents.
This included the development of multi-agency air quality cells (AQCs) to co-ordinate the acquisition, analysis and interpretation of air quality data at large-scale fires. They are a resource for the early, acute stage of a fire and not a mechanism for monitoring during an extended incident or into the recovery phase.
Arrangements have been made in England to bring together experts from the Environment Agency (EA), Public Health England (PHE) and the Met Office on a 24/7 basis to form an AQC for any major incident threatening significant air quality effects.
AQCs assess the potential impacts of a major incident and, if necessary, deploy field monitoring teams equipped with portable monitoring and sampling instruments. The field monitoring capability includes the use of Gasmet FTIR analysers (see box), which can measure multiple gases simultaneously, and identify and measure almost any gas.
The analysers were supplied by Gasmet’s UK representative Quantitech, which also provides training and servicing.
In July 2014, a large fire broke out at the Averies Recycling facility in Swindon and, as the situation developed, it became apparent there was the potential for an extended burn time with possible effects on the environment and public health.
A multi-agency tactical co-ordination group chaired by the police was therefore set up to co-ordinate the response. The EA and PHE representatives agreed to convene an AQC, and Swindon Borough Council was also invited.
Suitable monitoring locations were identified and air quality monitoring teams and equipment were deployed. The Met Office contributed air dispersion models to inform the locations, and it was necessary to relocate monitoring equipment as a result of changes in wind direction and plume behaviour.
In this case, the results continued to show a pattern of transient elevated spikes with levels consistently below national air quality standards so the decision was made to stand down the AQC. But it became apparent that fire fighters were unable to make progress due to the large volume and height of the compacted waste, around 10m high in places. It was therefore necessary for 3,000 tonnes of uncombusted waste to be removed from the site.
The site operator did not remove it by the deadline, so the EA used its powers to implement the clean-up operation nearly a month after the fire started. The waste was checked and dampened prior to being transported to the agreed landfill site for disposal.
Under normal circumstances an AQC would not be redeployed to the same site during a single incident. But it was agreed that because of the changes in the firefighting regime, a second AQC would be needed to assess the impacts on the plume and subsequent effect on public health.
The monitoring results indicated that, even when active firefighting started, the plume showed similar characteristics to that recorded during the first AQC period.
Summarising the advantages of portable FTIR analysers, Phil Chappell, air quality manager of the EA’s National Incident Management Services, said: “The Gasmet DX4030 instruments we procured in 2009 are a critical component of our air quality major incident response service.
“The ability to deploy quickly a single instrument capable of simultaneously identifying and determining the concentration of a wide range of gases is essential to the rapid assessment of the risk posed by large fires, such as the one at Swindon, to both public health and the environment.
The Gasmet FTIR analyser measures ambient gases, so non-heated versions (DX4030 or DX4040) are employed by AQCs and other hazardous incident investigation teams around the world.
Sample gas is drawn into the analyser which runs continuously, measuring timeweighted averages of user-definable length from one second to five minutes.
Capable of sub-ppm detection, the Gasmet FTIR analysers provide fast response times, which is essential for ‘time-urgent’ incident investigations. Zero calibration with clean air or nitrogen once a day is the only calibration required, so carrier gases, special test gases and other consumables are not needed.
The Gasmet analyser is often used in a table-top configuration but is also supplied with a backpack, so the user can move around looking for ‘hot-spots’.
With the standard gas library, the DX4040 is capable of detecting 25 gases simultaneously. But this can be enhanced with Calcmet Pro software, which gives the user access to a reference library of more than 250 gases and a 50 gas measurement capability, which is especially useful in situations where unknown gases are encountered.
Dominic Duggan is director of Quantitech