Air sampling is used to collect samples of airborne particles present in an environment. Analyses of the air samples can provide information concerning potential exposure to harmful respirable agents. Bioaerosol sampling can be used to identify particles of biological origin such as viable and non-viable fungal spores, bacteria, pollen, skin cells, fibers, and insect parts.
Until recently, analyses of bioaerosol samples typically involved directly counting the organisms in a sample, or indirectly by providing culture media in an environment and counting colony-forming units. While these methods provide reasonably adequate assessment of bioaerosol concentration, such methods are time-consuming (e.g., some analyses may take days or even weeks to complete) and may be unreliable. Recently, the threat of biological warfare and terrorist attack has prompted the development of highly sensitive molecular techniques for detecting microorganisms, such as polymerase chain reaction (PCR) and immunological assays.
Sampling devices that are currently used for collecting bioaerosols for subsequent analysis include filters, impingers, and impactors; however, such devices suffer from disadvantages that limit their use in assessing exposure to airborne bioparticulates. For example, samples extracted from filters are often insufficient for determining the concentration of bioparticulates in the air because of poor extraction efficiency. Impingers and impactors may be suitable for short-term sampling, but these devices cannot be used for long-term exposure assessment because of liquid evaporation in impingers and potential particle re-entrainment in impactors.
A sampling apparatus was developed that utilizes one or more cyclone separators to collect airborne particles from the atmosphere. The apparatus not only separates out aerosols from the atmosphere, but also serves as a collection tube for aerosol particles.
When sampling an environment, air from the surrounding atmosphere is drawn through the open end of the collection tube. The air entering the tube is directed to flow in a direction that is generally tangential to the inner surface of the tube, which causes the air to spiral toward the closed end of the tube to form an outer vortex. The airflow then spirals back toward the open end of the tube to form an inner vortex, and exits the tube through its open end. The velocity of the airflow exerts a centrifugal force on particles entrained in the air, causing them to impact the tube’s inner surface and separate from the airflow. Since the sample is collected directly in the collection tube, in situ analysis of the collected particles can be performed. Through its unique design, this apparatus can use the centrifugal force of the airflow on aerosolized particles, forcing them to separate by size.