Methods of Active Air Sampling

Impaction: This method uses a high-velocity air stream to impact the particles onto a solid or sticky surface, such as a glass slide or a Petri dish. 

• The particles are collected based on their inertia and size.
• Impaction is suitable for sampling larger particles (>1 µm) and viable microorganisms.

Impingement: This method uses a liquid medium, such as water or buffer solution, to capture the particles in a chamber or a nozzle.

• The particles are collected based on their momentum and solubility.
• Impingement is suitable for sampling smaller particles (<1 µm) and viable microorganisms.

Centrifugal: This method uses a rotating drum or a disc to separate the particles from the air stream by centrifugal force.

• The particles are collected on a filter or a culture medium attached to the drum or the disc.
• Centrifugal is suitable for sampling particles of various sizes and viable microorganisms.

Filtration: This method uses a porous membrane or a fibrous material to trap the particles as the air passes through it.

• The particles are collected based on their size and shape.
• Filtration is suitable for sampling particles of various sizes and non-viable microorganisms.
• These methods require a pump or a fan to draw a known volume of air through the sampling device.
• They also have different advantages and disadvantages in terms of efficiency, accuracy, and convenience.

The choice of the method depends on the purpose and the conditions of the sampling.

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