The Air Quality Standards (Scotland) Regulations 2007

13.  The requirements for minimum data capture and time coverage do not include losses of data due to regular calibration or normal maintenance of the instrumentation. Twenty-four-hour sampling is required for the measurement of benzo(a)pyrene and polycyclic aromatic hydrocarbons. With care, individual samples taken over a period of up to one month may be combined and analysed as a composite sample, provided the method ensures that the samples are stable for that period. Where the three congeners benzo(b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, are difficult to resolve analytically, they may be reported as sum. The Scottish Ministers shall endeavour, in so far as practicable, to undertake twenty-four hour sampling for the measurement of arsenic, cadmium and nickel concentrations. Sampling shall be spread evenly over the weekdays and the year. For the measurement of deposition rates the Scottish Ministers shall endeavour, in so far as practicable, to obtain monthly, or weekly, samples throughout the year.