At an incident involving hazardous chemicals, local fire and rescue services and police services can contact the Met Office, Environment Monitoring and Response Centre (EMARC). Typical scenarios could be a chemical spillage, a fire at a chemical plant or oil refinery or a road traffic collision in which a hazardous substance has been released. For small-scale events, EMARC produces meteorological guidance and a plume prediction as a chemical meteorology (CHEMET) report. For larger release events, such as the Buncefield Oil Depot fire, more sophisticated plume-modelling techniques are used.
A CHEMET report has two parts.
CHEMET Form A contains the input data, which consists of the incident details including grid reference of the location, time of the event and any additional information on the chemicals involved. If available it can also include details of the current weather at the site. The Form A is completed by the emergency services and forwarded to EMARC.
CHEMET Form B contains the weather forecast information along with an area at risk map. Image 6 gives one example of a risk map.
The advantages of using CHEMET are:
- Quick response – typically within 20 minutes of providing Form A information
- Delivered by fax or email
- Easily identifiable area of risk
- Sufficient for most short-lived incidents
The limitations of CHEMET are:
- It will not give information on chemical concentrations and therefore dilution down-wind
- It does not take into account extreme heat
- It does not take into account topography of the area (e.g. where the land down-wind is raised and thus has may divert the plume from the predicted area)
- No information is given on deposition
- It only provides ‘short period’ information; the wind direction or weather can change suddenly