Arsine is a colorless, highly toxic gas with the chemical formula AsH3. It forms when arsenic comes into contact with an acid or water, and it is one of the most dangerous industrial gases because of its ability to destroy red blood cells rapidly after inhalation. With a faint garlic-like or fishy odor detectable only at concentrations around 0.5 parts per million (ppm), arsine can reach lethal levels before a worker even notices it.
Chemical Properties
Arsine has a molecular weight of about 78 g/mol. At room temperature it exists as a gas, though it is commonly shipped in pressurized cylinders as a liquefied compressed gas. It is flammable. The odor is often described as mildly garlicky, but relying on smell for safety is unreliable because the gas can be present at harmful concentrations well below the detection threshold of the human nose.
Where Arsine Is Found
Most arsine exposure happens in two industries: semiconductor manufacturing and metals refining. In semiconductor fabrication, arsine is used deliberately as a source of arsenic for doping silicon wafers. In metals processing, it often appears as an unintended byproduct when arsenic-containing ores or metals come into contact with acids during smelting, galvanizing, or etching. This unintentional generation is what makes arsine especially dangerous: workers may not realize the gas is being produced until symptoms appear.
Less common sources include battery recycling operations, soldering with arsenic-contaminated materials, and certain chemical laboratory procedures. Any industrial process that combines arsenic (even as a trace contaminant in metal) with an acid or strong reducing agent can release arsine.
How Arsine Harms the Body
Arsine’s primary danger is massive hemolysis, the rapid destruction of red blood cells. Once inhaled, the gas enters the bloodstream through the lungs and attacks red blood cells directly, causing them to rupture. The contents of those ruptured cells then flood the bloodstream, and the kidneys must filter out the debris. This overload can cause acute kidney failure, which is the leading cause of death in arsine poisoning.
The destruction of red blood cells also releases hemoglobin into the urine, turning it dark red or brown, a sign called hematuria. Jaundice (yellowing of the skin and eyes) follows as the body struggles to process the breakdown products. In severe cases, the skin can take on a bronze discoloration. Blood counts continue to drop for several days after exposure, even with no further contact with the gas, because the damage to red blood cells is already set in motion.
Symptoms and Timeline
One of the most dangerous features of arsine poisoning is the delay between exposure and symptoms. Case reports consistently show a lag of 1 to 24 hours before the first signs appear, though in high-concentration exposures the delay can be as short as 1 to 3 hours. This means a worker could leave an exposure area feeling fine and not develop symptoms until they are at home.
The earliest symptoms are nonspecific: headache, malaise, chills, nausea, vomiting, and cramping abdominal pain. These are easy to dismiss as a stomach bug. Within hours, the hallmark signs emerge. Dark or red-colored urine is the most distinctive early warning. Chest pain, shortness of breath, and confusion can follow. Jaundice typically develops within 24 to 48 hours.
Even after a single acute exposure, the most serious effects can be delayed by days. Kidney failure may not become apparent until 2 to 3 days after the event. Long-term complications reported in survivors include nerve damage and neuropsychiatric symptoms that have appeared anywhere from 1 to 36 months after the initial exposure.
Diagnosis and Lab Findings
If arsine exposure is suspected, the key diagnostic test is a 24-hour urine collection for arsenic levels. Total urinary arsenic above 100 micrograms per liter is considered abnormal. Spot urine samples can be used in an emergency. Blood arsenic levels are less useful because arsenic clears from the bloodstream quickly, making the window for detection short.
Beyond arsenic levels, doctors look for laboratory signs of hemolysis: falling hemoglobin and hematocrit, elevated bilirubin (a marker of red blood cell breakdown), and free hemoglobin in the blood and urine. These hematologic markers may continue to worsen for several days after exposure, so repeated testing is necessary even when initial results seem mild.
Treatment for Arsine Poisoning
There is no antidote for arsine poisoning. Treatment focuses on supporting the body while it deals with the massive red blood cell destruction. The two primary interventions for severe cases are exchange transfusion, where a patient’s damaged blood is gradually replaced with donor blood, and hemodialysis to support failing kidneys. Both carry significant risks and do not always produce good outcomes.
Plasma exchange has also been used in severe cases. The overall prognosis depends heavily on how much arsine was inhaled and how quickly treatment begins. Because the most dangerous effects (especially kidney failure) can be delayed, anyone with a confirmed or suspected exposure needs close medical monitoring for several days, even if they initially feel well.
Workplace Safety Limits
The current OSHA permissible exposure limit for arsine is 0.05 ppm as an 8-hour time-weighted average. That is an extraordinarily low threshold, reflecting just how toxic the gas is. For context, you can smell arsine at roughly 0.5 ppm, which is already 10 times the legal workplace limit. The concentration considered immediately dangerous to life or health (IDLH) is just 3 ppm.
Because of these razor-thin margins, facilities that use or may generate arsine rely on continuous electronic gas monitoring rather than human senses. Fixed gas detectors, portable multigas monitors, and wireless sensor networks are standard in semiconductor fabs and smelting operations. These systems trigger alarms at concentrations well below the OSHA limit, giving workers time to evacuate before reaching dangerous levels. Proper ventilation, enclosed processes, and emergency air supplies are additional layers of protection in high-risk environments.