The capability to convene a multi-agency Air Quality Cell (AQC) was established in England in 2009 following the Buncefield Oil Storage Depot incident. A review of this event identified the need to rapidly co-ordinate the acquisition, analysis and interpretation of air quality data in major incidents. Arrangements have been made in England to bring together experts from the Environment Agency (EA), Public Health England (PHE) and the UK Meteorological Office on a 24/7, 365 days and year basis to form an AQC for any major incident threatening significant air quality impacts. The AQC will assess the potential impacts of a major incident and if necessary will deploy one or more of the four field monitoring teams equipped with portable monitoring and sampling instruments or one of two mobile laboratories. The field monitoring capability includes the use of Gasmet FTIR analyzers which provide the teams with the ability to measure multiple gases simultaneously with one instrument and to identify and measure almost any gas. The analyzers were supplied by Gasmet’s UK representative Quantitech, which also provides ongoing training and service.
On the night of 21 July 2014, a large fire broke out at a Recycling facility in Swindon. Initial reports from Wiltshire Fire and Rescue Service (WFRS) at the early stage of the incident indicated that hundreds of tonnes of waste was held on site and that there were no houses nearby. As part of the initial risk assessment, PHE chemical on-call staff began gathering information and subsequently identified (using GIS maps) that the immediate area (within 250m) of the incident was mainly industrial and commercial use, with the nearest residential properties being approximately 400m away from the incident. Users of the industrial and commercial units in the immediate vicinity of the fire were evacuated and public health messages were communicated to residents providing basic advice to shelter in order to minimise exposure to the smoke plume. At this early stage, a local tactical command structure had not been established and there was no information on the expected duration of the fire.
The EA and PHE were notified of the incident and discussed whether or not an AQC was required. AQC arrangements provide a mechanism to allow partner agencies to agree a common interpretation of the air pollution levels in the vicinity of major incidents; this is usually provided from a combination of air quality monitoring, modelling and expert judgement which is based on experience of previous comparable incidents.
The decision to convene an AQC is made jointly by the EA and PHE and will only be activated where: (a) there are potentially significant public health issues; (b) a suitable command and control structure is in place; and (c) the duration of incident is likely to be more than 8 hours. The AQC is chaired by the EA and the core membership includes scientists from PHE and the UK Meteorological Office. Where appropriate, local authorities, the Food Standards Agency and the Health and Safety Laboratory may be invited to participate.
Once established, an AQC typically operates for up to 3 days or until the acute phase of the incident is over, whichever is the shorter. The AQC partners, in discussion with any multiagency partners decide when to stand down, at which point the incident is usually handed over to the multiagency recovery group led by the relevant local authority.
If equipment is deployed, the AQC (usually the EA and PHE) decides on the monitoring locations, taking into account meteorological conditions and the location of nearby human receptors. The field monitoring teams carry a range of equipment including a particulate matter monitor and a Gasmet FTIR analyzer to measure a variety of volatile air pollutants. Dependent on the nature and profile of the fire, a mobile laboratory can be deployed to provide more detailed air quality data than the portable equipment, as was the case for this incident.
The Gasmet FTIR analyzers measure ambient gases, so non-heated versions (DX4030 or DX4040) are employed by the AQC and by other hazardous incident investigation teams from around the world. Sample gas is drawn into the FTIR analyzer with a built-in pump through a handheld particle filter and Tycon tubing. The analyzer runs continuously, measuring time-weighted averages of user definable length from one second to five minutes. Capable of sub-ppm detection limits without using sorbent traps for sample pre-concentration, the Gasmet FTIR analyzers 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.