Is the birch pollen threat the same indoors and outdoors?

The study compares the concentration of birch pollen indoors and outdoors in 2019. The investigations were carried out using the volumetricmethod (Hirst type pollen sampler). Seasonal Pollen Index (SPI) was estimated as the sum of daily average pollen concentrations in the givenseason. Pollen season was defined as the period in which 98% of the annual total catch occurred. The birch pollen season in 2019 started at thebeginning of April. The first pollen grains were recorded in internal samples on the April 4^th, only one day after than in external air. In generally theperiod of occurrence of birch pollen in the outdoor and indoor air coincided (28/29 days). The maximum values of seasonal birch pollen countwere noted on April 18^th (467 g/m³) and on April 20th (1971 g/m³) (indoor/outdoor). The annual pollen sum of birch noted outdoor reached 18 148, inside seminary room – 3141, which is 17% of total. Three peaks of high concentrations of birch pollen were noted outside, which was only partly reflected in the indoor air. This may be result of closing the windows for the night and on weekends. The threat of birch pollen allergens during the 2019 pollen season was high. For most of the season in outside air were noted values in which patients report severe allergy symptoms. Such concentrations were recorded for 9 days indoor with concentration above 90 grains/m³ (acute symptoms of allergy).