Broiler embryos and chicks were exposed to formaldehyde vapors (up to 130 ppm) during the final 3 days of incubation. Bacterial load was significantly lower in a formaldehyde-fumigated hatcher than in an unfumigated hatcher. Hatchability was not affected. To determine if exposure to formaldehyde vapors in the hatcher would affect broilers' ability to tolerate variations in air quality, chicks were placed in either adequately or poorly ventilated confinement facilities for 45 days. Total and respirable dust particles (< or = 5 microns in diameter) increased to a greater extent between 5 and 6 weeks of broiler age in the poorly ventilated facility than in the facility with adequate ventilation. Mortality at 6 weeks of age was significantly higher in broilers exposed to formaldehyde in the hatcher and housed with poor ventilation than in broilers exposed to formaldehyde and raised with adequate ventilation. Six-week body weight, feed conversion, and septicemia/toxemia condemnations were adversely affected by poor ventilation. This study found that the quality of air in the confinement facility had a greater influence on broiler productivity than did exposure to formaldehyde vapors in the hatcher.