Pollen, dust, fungi, industrial pollutants, and general vehicle exhaust are common outdoor sources of indoor air pollution. Other sources include exhaust from vehicles on nearby roads or in parking lots or garages, loading docks, odors from dumpsters, unsanitary debris near outdoor air intakes, and cigarette smoke from office workers now required in most cities to take their cigarette breaks outside of building entrances. Another source is exhaust from the building itself or from neighboring buildings that is re-entrained, or drawn back into the building.
This most common of representations and warranties is most often abused. Buyer or tender may initially want a flat representation that there are not now and never have been any Hazardous Materials on the premises or any operations that generate, use, treat, store, or dispose of Hazardous Materials. Difficulties that immediately arise include the length of time this representation will reach back, the de minimis without a qualifier based on the best knowledge.