Hydrazines (1,2-dimethylhydrazine; 1,1-dimethylhydrazine; hydrazine) are extremely toxic nitrogen compounds that are colorless and have an ammonia or fish-like odor. Hydrazine is used in many industries including petroleum refining, photographic processing, semiconductor manufacturing, soldering, and weapons manufacturing. Hydrazines are also a component of rocket fuel and, in addition, can be found in certain medications, including hydralazine, isoniazid, and phenelzine. Gyromitra spp. mushrooms contain the toxin gyromitrin, which is metabolized to monomethylhydrazine. Hydrazines are sometimes found at hazardous waste sites. Hydrazine exposure may occur via aerosol inhalation, liquid ingestion, or dermal absorption. The consequences of exposure are severe and may include death.

Aerosol exposure and inhalation include irritation of the eyes, nose, throat and skin, dyspnea, dizziness, and nausea. Direct contact with the liquid form can produce chemical burns of the skin, eyes, and mucous membranes.

After inhalation or absorption of large quantities of hydrazine, there may be lethargy, confusion, tremors, seizures, coma, and death. Delayed findings may include hepatitis, nephritis, pulmonary edema, liver necrosis, and GI hemorrhage. Seizures may also occur after prolonged exposure. Severe renal damage, possibly secondary to hemolysis, may occur. Kidney damage is usually less severe than hepatic effects.

The Immediately Danger to Health or Life (IDHL) air concentration of hydrazine is 50 ppm. The National Institute of Occupational Safety and Health (NIOSH) considers hydrazine a potential carcinogen.