Slit
Sampler - Slit sampler is an efficient and convenient device for the enumeration of bacteria carrying particles in a unit volume of air. It was introduced by Bourdillon et al. in 1941. It works on the principle that when air is drawn from the environment at a fixed rate and the suspended particles are allowed to impinge on the surface of an agar plate, on incubation each particle will form a colony.
The equipment consists of a box closed by an air tight door. There is a slit of 0.33 mm width and 27.5 mm length with vertical parallel sides of about 3mm deep at the top through which the sampled air enters. The box is connected to a suction pump which maintains it at a negative pressure of 22.6 mm mercury. At the correct negative pressure air will enter through a slit of above dimension at the rate of one cubic foot (28.3 lit.) per minute.
