• Improper ventilation
• Mold
• Finished basements and crawl spaces with moisture • Interior French drains
• Leaks from storms, plumbing, gas lines
• Improperly functioning furnace, hot water tank or other appliance • Improperly installed gas appliances
• Previously performed pesticide application
• Cleaning chemicals
• Leaking stored chemical containers
• Artificial fragrance
• New carpet, cabinets and other materials
• Bird, pet and other dander and fecal matter
• Sewage backups and leaks
• Radon
• Asbestos