I diden't think it was too bad at first... untill I used it to seal the entire in side of a boat hull. It took about 4 oz of the stuff. After a while even my stomach started to turn. I plan to install a exaust fan in my work shop and see if it helps next time. When I told my wife that the stuff was alot cheaper she told me that SHE would pay the difference!!! I have yet to see that!