The development of sampling methods for the assessment of indoor bioaerosols

Airborne bioaerosols form a large component of the indoor domestic environment and their presence, growth and dispersion are often influence by heating, ventilation, air conditioning and humidifier systems. The most common microorganisms may cause respiratory disease and allergic reactions in susceptible individuals. Sampling methods amenable to standardisation have been developed for the characterisation of indoor bioaerosols. A major objective of this study was to develop cyclone samplers that collect bioaerosols in size ranges that reflect those collected in the human respiratory system, and have minimal effect on their culturability. The physical collection characteristics and bioefficiency of the sampler systems were assessed. A induced-size version of a well-characterised cyclone sampler, with a 50% collection ( d 50) of 0.8 μm aerodynamic diameter, was identified as the basis for a sampling and collection system suitable for characterising indoor bioaerosols. A series of single-stage inertial impactors was designed to size-separate the aerosol entering the cyclone. Additional wind tunnel efficiency tests showed that d 50 values for these size-separators were 3.5 and 4.7 μm, respectively. Five species of microorganisms were used to determine the bioefficiency of (a) the cyclone sampler and (b) the cyclone sampler coupled with a pre-separator impactor. All but Penicillium expansum spores suffered damage during aerosolisation decreasing their culturability by several orders of magnitude, compared with culturability prior to aerosolisation. The reduced-sized cyclone sampler had satisfactory sampling and collection efficiencies, and could “gently” collect different commonly found indoor bioaerosols for subsequent analysis.