Birch pollen and antigens were collected on sampling tape of the Burkard Seven-day-recording Pollen and Spore Trap before, during and after the pollen season. The antigens were then transferred to a polyvinylidene difluoride (PVDF) membrane. For detection and quantification of the antigens a double antibody system and chemiluminescence was used. The chemiluminescence-chemicals emit light at positions in the membrane where antigen is present. The light produced was documented by contact of the blotting membrane with x-ray film, and also measured with a newly developed luminometer. Birch pollen antigenic activity was found on the tapes a few weeks before the local incipient birch pollen season although no birch pollen grains were monitored on a control tape for allergy information service. The concentration of small antigenic particles present in the air after rainfall is discussed.