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Notes: Background Occupational exposure to rodent allergens may cause laboratory animal allergy. Personal exposure to occupational allergens is measured by collecting airborne dust on filters using person-carried pumps. This technique cannot be used to evaluate personal protective respiratory equipment. Recently developed intranasal air samplers collect inhaled particles by impaction on adhesive strips within the samplers.Objective The aims were to compare rodent aeroallergen exposure assessment using nasal air samplers with personal air sampling, and to evaluate the efficacy of using respiratory protection during rodent work using nasal air samplers.Methods Aeroallergen exposure was assessed during rodent work using both nasal air samplers and personal air samplers. The efficacy of respiratory protection (P2 facemasks and fresh-air helmets) was studied in subject pairs working side by side, one person with protection, the other without. Right nostril samples were laminated with protein-binding membrane and immunostained for rat urinary allergen-containing particles. Left nostril samples and air samples were eluted in buffer and analysed in amplified ELISAs for rat (RUA) and mouse (MUA) urinary allergen content (detection limit 10 pg/mL). Allergen collection efficacy of the nasal air samplers was tested at high and low exposure levels and at different flow rates using static sampling.Results P2 facemasks decreased the amount of inhaled allergen by about 90%, and very little allergen was inhaled using fresh-air helmets. Allergen levels in air and nasal samples correlated well (rs was about 0.8 for both RUA and MUA). The number of RUA-positive particles and nasal allergen levels measured in ELISA also correlated significantly (rs = 0.8). Collection efficacy of the nasal air sampler was better during high exposure (cleaning cages, median 73% of allergenic particles collected), than during low exposure (undisturbed room, 49% of particles).Conclusion Nasal air sampling is a relevant and sensitive complement to personal air sampling and enables evaluation of personal respiratory protection equipment. Use of P2 facemasks and fresh-air helmets may substantially reduce occupational exposure to inhaled allergens.