Polyurethane floor-finishing products contain chemical compounds that can cause short- or long-term adverse health effects. Some of these compounds are problematic when they come into contact with the skin, and some are harmful when they're inhaled.
Potentially Harmful Compounds
One category of these compounds is referred to as volatile organic compounds, or VOCs, and they evaporate into the air when the finishing product is wet and as it cures. Some VOCs commonly found in polyurethane finishes include xylene, ethylbenzene and acetates.
Polyurethane finishes also include chemicals called diisocyanates, which also become airborne during the application of the finishes and are known to cause health problems.
The VOCs and other potentially dangerous chemicals in polyurethane products can have a negative health impact in both the near term and the long term. Direct contact with the chemicals can cause skin irritation, and exposure to the vapors during installation and before the finish cures may cause eye, throat and nose irritation, breathing difficulties, headaches, nausea, asthma attacks or dizziness.
Prolonged exposure to these chemicals, as in those who work with the finishes regularly, may cause chronic lung conditions, birth defects, allergies, cancer or other serious problems.
Water-Based and Oil-Based Finishes
Water-based polyurethane finishes may contain fewer VOCs than oil-based finishes, in which the VOCs are used as solvents. Most water-based finishes still contain some level of VOCs, however, and all polyurethane products contain diisocyanates.
Vapors and Curing
Once the polyurethane finish has dried and cured, it is generally considered to be safe, but during the drying and curing process, the finish releases potentially harmful chemicals into the air via evaporation, a process called off-gassing. Depending on the product applied, the temperature and humidity conditions in which it was applied, and the ventilation of the room where it was applied, off-gassing of polyurethane finishes can continue for a period of time ranging from days to months.
To minimize the dangers of polyurethane vapors, always apply the finishes in a well-ventilated space, wear a face mask and eye protection and don't smoke. If your floor is being finished by a professional and it's possible for you to leave the home, it's best to stay away long enough for the finish to cure and the odor to disperse, which usually takes about 48 hours.
To speed up the drying and curing process and reduce the off-gassing period, ensure that the room remains well-ventilated. Opening windows can speed up the process, but it can also admit dust that may contaminate the floor's finish. Instead, try increasing air flow by setting up fans to blow across the floor, and turn up the heat in the room to accelerate drying.