Design and validation of a high-flow personal sampler for PM2.5

A high-flow personal sampler (HFPS) for airborne particulate matter has bee n developed and fully characterised, and validation tests have been carried out. The sampler is a low-cost gravimetric instrument designed to collect particulate matter with a 50% cut point at 2.5 mum aerodynamic equivalent d iameter (PM2.5), where size selection is achieved by the use of porous poly urethane foam. Development of a porous foam selector was chosen over a cycl one or impactor due to the lightweight, low-cost, and compact design that c ould be achieved. The sampler flow rate of 16 l/min is achieved using a por table, flow-controlled pump; this flow rate is far higher than that of conv entional personal samplers and the HFPS can therefore be used for personal sampling in the ambient environment over short sampling periods of much les s than 24 h. The HFPS is currently being used in a study of particle exposu re of urban transport users (cyclists, car drivers, bus and Underground rai l passengers) where personal sampling over short time periods representing typical commuter journey times is required. The HFPS was fully characterise d in chamber studies with a TSI aerodynamic particle sizer (APS). The sampl er was then validated against a co-located U.S. EPA Federal Reference PM2.5 Well impactor Ninety Six (WINS) and a KTL cyclone, and parallel testing wa s performed. Initial testing showed some penetration of particles through t he porous foam structure; applying an oil coating to the foam eliminated th is problem. Chamber testing was carried out on a number of different select or prototypes, with the final design giving a 50% penetration diameter (i.e ., d(50)) of 2.4 mum at 16 l/min. The new sampler exhibited good agreement in three sets of co-located tests with established samplers, and parallel t esting showed excellent agreement between paired HFPS samplers.