Shown is a Burkard Pollen and Spore collector. The slotted component at the base contains a turbine which sucks air through the upper cylindrical chamber.
Pollen grains and mold spores enter the chamber through the slot in its side.
A Swiss clock movement moves a silicone-greased glass slide slowly past the slot over a 24 hour period.
The upper chamber is on ball bearings and constantly faces upwind. The "visor" above the slot is a rain shield to prevent water from flooding onto the slide.
After 24 hours the slide is removed, revealing a swath of pollen which has been collected over a 24 hour period.
The slide is then stained with a red dye (Calberla's solution). The pollen grains appear as pink blobs in the photomicrograph at right, but can be identified accurately at higher magnification.
Pollen grains and mold spores are systematically counted.
The count is reported as pollens (or mold spores) /cubic meter of air/24 hours.