Most hardeners react wit air. So buy in small amounts and keep it tightly sealed. BTW it's usually a chemical called diisocyanate. Diisocyanates are a group of low-molecular-weight aromatic and aliphatic compounds. The most common of these are toluene diisocyanate (TDI), methylene bisphenyl isocyanate (MDI), and hexamethylene diisocyanate (HDI). Not that they aren't dangerous substances, because they are, I just wanted to make sure you guys know that it isn't cyanide gas your spraying around everywhere. Isocyanates are used for a ton of things. They are most likely in the insulation in your house if it's a newer one. The Isocyanates are a stablized by adding a catalyst that causes a bond to another type of molecule rendering them harmless for the most part. It's the free form of these types of Isocyanates that creates harmful effects.
TDI and other isocyanates are powerful irritants to the mucous membranes of the eyes and gastrointestinal and respiratory tracts. Direct skin contact with TDI can also cause marked inflammation. Respiratory irritation may progress to a chemical bronchitis with severe bronchospasm with prolonged exposure. Sporadic cases of hypersensitivity pneumonitis (HP) have also been reported in workers exposed to isocyanates. Individuals with acute HP typically develop symptoms 4 to 6 hours after exposure. Symptoms are often flu-like, with fever, muscle aches, and headaches. Symptoms may also include a dry cough, chest tightness, and difficult breathing. Individuals with chronic HP often experience progressively more difficult breathing, fatigue, and weight loss. If you begin to expierence these types of symptoms it means you need to check your work area and equipment. The ventilation in your work area may not be adequete to keep the PPM down to a number that your respirator can safely filter out, OR your respirator protection is inadequete. If you so much as think your respirator is not protecting you it's important that you stop using the 2 part urethanes until you can get filters that are at least P100 compliant. Better yet is a fresh air supply mask. This is simply a hose apratus connected to your mask to draw prefiltered air from a source that has been isolated from the work area. This is the easiest, cheapest, and best way to avoid exposure to Isocyanates.
I hope my Blabbering has helped clear up some confusion about these substances.
