Air sampling techniques- Part I

 

Air sampling is the enumeration of microorganisms present in air using various techniques. It is useful in disease forecasting, especially in plants. Based on the principle, air sampling techniques can be divided as follows. 

I)  Settling under Gravity

Egs: 1. Hesse’s tube  

         2. Settle plate method

II) Impaction

Impaction is of two types. One based on centrifugal action and another one based on impingement onto solid.

a)    Centrifugal action

Egs: 1. Air Centrifuge

        2. Reuter centrifugal air sampler

b)     Impingement on to solids

Egs: 1. Hollaender & Dalla valle sampler

        2. Slit sampler

        3. Sieve sampler

        4. Andersen six stage or multistage sampler

III) Filtration 

Egs: 1. Tube sampler

        2. Millipore filter

IV) Impingement into liquids

Egs: 1. Raised impinger

        2. Bead bubbler device

        3. Lemon sampler

V)  Electrostatic forces

Egs: 1. Litton large volume air sampler