Design of an environmentally controlled rotating chamber for bioaerosol aging studies

Abstract

A chamber was designed and built to study the long-term effects of environmental conditions on air-borne microorganisms. The system consists of a 55.5-L cylindrical chamber, which can rotate at variable speeds on its axis. The chamber is placed within an insulated temperature controlled enclosure which can be either cooled or heated with piezoelectric units. A germicidal light located at the chamber center irradiates at a 360° angle. Access ports are located on the stationary sections on both ends of the chamber. Relative humidity (RH) is controlled by passing the aerosol through meshed tubes surrounded by desiccant. Validation assay indicates that the interior temperature is stable with less than 0.5 °C in variation when set between 18 and 30 °C with the UV light having no effect of temperature during operation. RH levels set at 20%, 50% and 80% varied by 2.2%, 3.3% and 3.3%, respectively, over a 14-h period. The remaining fraction of particles after 18 h of suspension was 8.8% at 1 rotation per minute (rpm) and 2.6% at 0 rpm with the mass median aerodynamic diameter (MMAD) changing from 1.21 ± 0.04 μm to 1.30 ± 0.02 μm at 1 rpm and from 1.21 ± 0.04 μm to 0.91 ± 0.01 μm at 0 rpm within the same time period. This chamber can be used to increase the time of particle suspension in an aerosol cloud and control the temperature, RH and UV exposure; the design facilitates stationary sampling to be performed while the chamber is rotating.

Generic aspects of the airborne spread of human pathogens indoors and emerging air decontamination technologies

“…13 The equipment must also simulate naturally occurring environmental conditions and the duration of exposure to accurately assess aerosol survivability. 24 Various analytical methods and air samplers have been used to characterize airborne pathogens and overcome the challenges of collecting and analyzing them. Relevant studies have been reviewed in detail elsewhere.…”

Resistance of Aerosolized Bacterial Viruses to Relative Humidity and Temperature

“…To evaluate the effects of temperature and relative humidity on the infectivity of airborne phages, RH levels of 20% (low) and 50% (medium) were assayed at 18°C, whereas an RH of 80% was assayed at 18°C and 30°C. The desired levels of RH were obtained by passing the aerosol through various desiccant-filled pipes (17). At 18°C, 20% RH was obtained by passing the aerosol through 60 in.…”

“…The specifications and a detailed description of the aerosol chamber used in this study are available elsewhere (17). Briefly, the aerosol chamber is a 55.5-liter aluminum rotating drum sheltered inside an insulated temperature-controlled enclosure.…”

“…The mass median aerodynamic diameter (MMAD) was 1.12 Ϯ 0.05 m immediately after nebulization. The variations in particle concentrations and MMADs over time inside the chamber were described previously (17).…”

“…Here, we investigated the infectivity of phages following exposure to environmental stress in the airborne state using a newly designed rotating environmental chamber (17). Four phages were aerosolized at various temperatures and levels of relative humidity (RH) and exposed to UV radiation.…”