Automatic Hydrocarbon Network
Automatic hourly measurements of speciated hydrocarbons, made using an advanced automatic gas chromatograph (VOCAIR), started in the UK in 1992. By 1995, monitoring had expanded considerably with the formation of a 13-site dedicated network measuring 26 species continuously at urban, industrial and rural locations. Currently there are 4 sites measuring 29 species continuously at urban and rural locations using an advanced automatic Perkin Elmer gas chromatograph.
What is measured?
|Parameters Measured||Monitoring sites and data|
cis-2-pentene (VOC-AIR only)
3-methylpentane (VOC-AIR only)
2+3-methylpentane (VOC-AIR only)
|Current sites: 5
Total sites: 18
Data availability: 01/01/1993 to 06/12/2023
Sources of VOCs
Non-Methane Volatile Organic Compounds (MNVOCs) often referred to simply as VOCs are emitted to air from a wide variety of sources. The National Atmospheric Emissions Inventory (NAEI) estimates emissions of NMVOCs for the UK, including information for benzene.
Health Effects of Benzene and 1,3-Butadiene
The International Agency for Research on Cancer (IARC) has determined that benzene and 1,3-butadiene are carcinogenic to humans. Details of the assessment of the carcinogenicity of these VOCs carried out by IARC can be found online.
What is the purpose of the network?
The focus in this measurement programme is two-fold: firstly to assess ambient concentrations of a range of Volatile Organic Compounds (VOCs) with significant photochemical oxidant forming potential, and secondly to measure benzene for comparison with the Ambient Air Quality Objectives and 1-3 butadiene for comparison with UK Objective.
How is the network run?
The automatic hydrocarbon monitoring network, as originally constituted, used state-of-the-art measurement techniques, combined with advanced software techniques for signal processing and validation. It was the first network of its kind in the world. The Automatic Hydrocarbon Network operated successfully for 10 years before the programme was re-focussed, re-designed and simplified in 2002.
By 2008, the UK Automatic Hydrocarbon Network consisted of five sites, located at Glasgow, Harwell, London Eltham, London Marylebone Road and Auchencorth Moss. In 2011, the analyser at Glasgow was replaced with a non-automatic sampler reducing the number of sites to 4. The Harwell instrument was relocated to Chilbolton Observatory at the start of 2016.
The four monitoring stations are fitted with automatic Perkin Elmer gas chromatographs measuring a wide range of VOCs, equivalent to that studied under the original measurement programme. These instruments are capable of measuring and reporting at least 29 hydrocarbons.
Measurements from all four sites are reported to the European Commission, satisfying requirements under the Ozone Daughter Directive, later superseded by the Ambient Air Quality Directive for monitoring photochemical ozone precursor VOCs. Corresponding benzene and the 1,3-butadiene data are used for comparison with the UK Air Quality Objectives, whilst benzene data are reported to the European Commission to fulfil requirements of the Air Quality Directive.
Air Quality data measured at both Auchencorth Moss and Chilbolton Observatory are reported to the EBAS database hosted by the Norwegian Institute for Air Research (NILU) for use on both the EMEP and ACTRIS projects.
View data for sites in this network
Data can be downloaded from the Data Selector section of this website.