AIR POLLUTION | MONITORING When reception staff at a central Birmingham office complained of a persistent smell of exhaust fumes, sensors were deployed to pinpoint the source of potential pollutants. Dr Peter Walsh, technical director at WSP, explains EMISSION CREEP R eception staff in a groundfloor, city centre office in Birmingham had complained of the persistent smell of vehicle exhaust throughout the working day. The building entrance a glass-fronted lobby with an automatic, wideaperture, opening front door had no doubledoor system, and there were gaps between the bottom and top of the front doors. Elevated pollutants were suspected to be present within the reception area, as a result of intrusion of street-sourced pollutants via the front doors continuous opening, and/or gaps around the bottom and top. The main source of the nitrogen dioxide (NO2) was suspected to be emissions from queuing taxis and other traffic immediately outside the reception lobby. To determine whether reception staff were being exposed to a high level of pollutants, a short monitoring campaign was undertaken, examining the extent of any exposure and, potentially, identifying the source type. Standard NO2 concentration Comment Guidance document Occupational long-term exposure limit 955 g.m-3 Eight-hour time-weighted average TFL PR703 A1 HSE CD283 Occupational short-term exposure limit (STEL) 1,910 g.m-3 15-minute average TFL PR703 A1 HSE CD283 1hr mean in ambient air 200 g.m-3 1 hr mean; not to be exceeded Air Quality Standards more than 18 times per year Regulations 2010 Annual mean in ambient air 40 g.m-3 Annual mean Table 1: Air-quality standards for NO2 Air Quality Standards Regulations 2010 Workplace exposure limits air-quality guidance Exposure to NO2 is governed by the Control of Substances Hazardous to Health (COSHH) regulations; however, there is no workplace exposure limit (WEL) for NO2 in HSE EH40/2005 Workplace Exposure Limits Second Edition. So, exposure to nitrogen dioxide should be kept as low as reasonably practicable, though current draft WELs have been applied in this instance.1 Ambient air-quality standards for NO2 are applicable in the ambient atmosphere (external areas) where the public may reasonable gain access. Air-quality sampling A continuous nitrogen dioxide monitoring device a Zephyr, manufactured by Earthsense was used to determine NO2 concentrations in the New Street office. The device, an electro-chemical sensor, is capable of logging NO2 concentrations every second. As an indicative monitor, its primary use was to provide a record of high-resolution trend data, and any inference of absolute nitrogen dioxide concentrations it provided was avoided. In the latter part of the survey, a series of diffusion tubes were deployed inside and outside the reception area. Diffusion tubes are a reliable monitoring method, and their use helps validate absolute NO2 concentrations. When combined with high-resolution data from the electrochemical sensor, a comprehensive record of NO2 concentrations and their variations can be obtained. To represent the exposure patterns of the reception staff, the electro- 38 October 2019 www.cibsejournal.com CIBSE Oct19 pp38-40 Birmingham .indd 38 20/09/2019 16:18