Key Facts 

Safety notice: Arsine is an extremely toxic gas that can injure workers before they notice anything is wrong. This article is an industrial hygiene reference, not medical guidance. Anyone who may have been exposed needs immediate professional medical attention, and the site emergency procedure should be activated at once. 

What is arsine gas? 

Arsine is an inorganic hydride of arsenic: a colorless gas at room temperature that is compressed into cylinders as a liquefied gas. It is toxic at concentrations far below those people can perceive, and it burns. In industry it is handled almost exclusively in the electronics sector, but it can also appear unexpectedly wherever arsenic-bearing material meets acid or moisture. For EHS teams, the practical problem is that the people most at risk often do not know if the gas is present. 

Identification 

Synonyms include arsenic hydride, arsenic trihydride, and hydrogen arsenide. Identifiers to confirm on any SDS or shipping paper: 

• Formula: AsH₃ 

• CAS number: 7784-42-1 

• UN number: 2188 (toxic gas, flammable) 

• Transport: shipped as a compressed, liquefied gas; the Emergency Response Guidebook entry for UN 2188 is the standard first-responder reference 

Cross-check these against the supplier’s SDS, since a mismatch between label, SDS, and inventory record is itself a finding worth correcting. 

Physical properties 

Only properties that change how you control the hazard are listed here. 

Values to be verified against NIST WebBook or the current SDS before publication. 

Odor is not a reliable warning. 

This is the most worth repeating to new staff. Arsine is often described as smelling garlic, but the odor is generally reported only at concentrations above the OSHA PEL. By the time someone notices it, they are already breathing more than the legal limit. 

Three further problems make smell useless as a safety check: 

1. Not everyone can detect it, and sensitivity varies from person to person. 
2. Olfactory fatigue can dull perception during continued exposure. 
3. A “no smell” conclusion is meaningless, because harmful concentrations may be present without any noticeable odor. 

Workplace decisions should rest on calibrated gas detection, not on anyone’s nose. 

Where does arsine exposure occur? 

Exposure falls into two groups: planned use in controlled processes and accidental generation, which is the harder one to manage because nobody expects it. 

Intentional use: semiconductor manufacturing 

Arsine supplies arsenic for doping silicon and germanium and for growing gallium arsenide and related compound semiconductors by epitaxial processes such as MOCVD. Those materials go into LEDs, laser diodes, high-frequency devices and some photovoltaic cells. Usage per tool is small, but cylinder change-outs, line purges and maintenance are the moments when releases happen. 

Unintentional generation 

Arsine forms when arsenic or arsenic compounds are reduced by nascent hydrogen, which is what happens when acid or water contacts certain metals or residues. Because it is a by-product, it is often missed in hazard assessments. Situations worth scanning for: 

A useful screening rule: if arsenic is in the material stream, and acid or moisture is anywhere nearby, assume arsine is possible until monitoring shows otherwise. 

Workers at risk 

• Semiconductor process and maintenance technicians 

• Smelter and refinery workers 

• Metal recyclers and scrap handlers 

• Gas-cylinder handlers, delivery drivers, and gas-room staff 

• Anyone doing maintenance, cleaning, or turnaround work where arsenic-bearing material is present 

What are the health effects of arsine exposure? 

This section is meant to help supervisors recognize a problem and escalate it. It does not describe treatment, which belongs to qualified medical providers. 

1. Mechanism: hemolysis 

Inhaled arsine enters the bloodstream and attacks red blood cells, which break apart (hemolysis). The released hemoglobin and cell debris can then overload and injure the kidneys. That chain of events—lungs, red cells, and kidneys—is why blood and kidneys are listed as the target organs. 

2. Delayed onset is a critical hazard. 

A worker can leave a contaminated area feeling fine. Serious effects may develop hours later, and the first symptoms can be vague. Two consequences follow for programs: 

• Feeling well after a suspected exposure does not mean the person is safe, so medical evaluation should not wait for symptoms. 

• Prevention has to rely on air monitoring and exposure controls, because symptoms arrive too late to serve as a warning. 

Specific time windows are intentionally omitted here until they are confirmed from an authoritative source. 

3. Signs of exposure to recognize and escalate 

Any of the following in someone who may have been near Arsine should be treated as a reason to escalate immediately: 

• Headache 

• Dizziness 

• Shortness of breath 

• Nausea 

• Abdominal pain 

• Dark or red-brown urine 

• Yellowing of the skin or eyes (jaundice) 

This is a recognition list, not a diagnostic or staging tool. 

4. Long-term exposure and carcinogenicity 

Repeated or prolonged exposure to arsenic compounds is associated with systemic effects, and carcinogenicity statements need careful wording. Agencies such as IARC and NTP classify arsenic and inorganic arsenic compounds as human carcinogens. Those classifications should be attributed to the issuing authority and not restated as “arsine is a human carcinogen.” Check how the current SDS and each agency address arsine specifically before making a claim in your own documents. 

What is the exposure limit for arsine? 

The OSHA PEL is the enforceable workplace limit. 

Not every number you encounter carries the same weight: 

• OSHA PEL: the legally enforceable U.S. occupational limit. 

• NIOSH REL: a recommendation from a research agency; not enforceable on its own. 

• ACGIH TLV: a professional guideline, often more conservative, that employers may adopt voluntarily. 

A site can have internal limits stricter than the PEL, but the PEL remains the compliance floor in the United States. 

Arsine exposure limits 

NIOSH also publishes an IDLH value (3 ppm, to be confirmed in the current Pocket Guide), which is a respirator-selection and emergency-planning benchmark and not an exposure limit. 

Detection and monitoring 

Because odor fails as a warning, detection has to be instrumented. Common elements of a monitoring approach: 

• Continuous fixed-point monitoring near cylinders, gas cabinets, process tools and exhaust 

• Electrochemical sensors, or other sensor technologies suited to arsine, with documented calibration and bump-testing 

• Audible and visual alarms linked to automatic responses where the process allows 

• Personal monitoring for non-routine tasks such as maintenance and cylinder changes 

• Awareness of cross-sensitivity, since other hydride gases can trigger some sensors 

Alarm setpoints should come from a facility-specific risk assessment, the sensor’s capabilities and applicable regulations. They should not be copied from a single guideline value. 

How is arsine controlled in the workplace? 

The hierarchy of controls applies directly: the earlier the control, the less you depend on people behaving perfectly. 

Elimination and substitution 

• Use alternative arsenic sources where the process chemistry allows it, such as liquid organoarsenic precursors that carry different hazards 

• Redesign processes so less gas is on site or in the line at one time 

• Prefer sub-atmospheric delivery packages, in which the gas is held below atmospheric pressure, so a breach draws air in and does not push gas out 

Substitutes carry their own hazards, so each one needs its own assessment. 

Engineering controls 

This is where most of the risk reduction happens: 

• Ventilated gas cabinets with dedicated exhaust 

• Restricted-flow orifices to cap the release rate from a cylinder 

• Continuous gas monitoring tied to alarms 

• Automatic, interlocked shutoff on detection or loss of exhaust 

• Exhaust-gas treatment (scrubbing or abatement) before discharge 

• Cylinder storage that is segregated, secured, and separated from incompatible materials 

• Process containment, welded or closed piping, and leak-tested connections 

Any airflow or capture figure should come from a specific standard or equipment specification for that application and not from a generic rule of thumb. 

Administrative controls 

• Written operating procedures for normal and abnormal operation 

• Detailed cylinder change-out procedures, including leak checks and purge steps 

• Maintenance procedures with line-breaking and decontamination steps 

• Permit-controlled work for non-routine tasks and confined or enclosed spaces 

• Exposure monitoring and incident records 

• Occupational health and medical surveillance run by qualified providers; test panels and schedules should be set by them 

• Training that covers the odor problem and delayed symptoms 

Respiratory and dermal protection 

Protective equipment is the last line of defense. Arsine is mainly an inhalation hazard, so gloves and clothing are not the main protection against the gas itself. Where respiratory protection is needed, it must be selected and managed under a compliant program (for U.S. employers, 29 CFR 1910.134). Because of the toxicity and poor warning properties, supplied-air or self-contained breathing apparatus is typically what high-hazard tasks and emergency entries call for, and air-purifying respirators should be considered only with expert guidance. 

Emergency response 

Keep the on-site message short enough to remember: 

1. Evacuate the affected area and move away from the release, upwind where appropriate. 
2. Do not re-enter without authorization and appropriate protection. 
3. Activate the site emergency response procedure. 
4. Treat any suspected exposure as a medical emergency. 
5. Give the responding medical personnel the arsine SDS. 

What the Arsenic SDS should tell you 

Treat the arsine SDS as an operational reference covering hazards, exposure controls, storage requirements, and emergency information. Reading it once at purchase is not enough; it should be reviewed when processes change and when the supplier issues a revision. 

Section 2: Hazard identification 

Check the GHS classification, signal word, pictograms, hazard statements, and precautionary statements. Supplier SDSs commonly show a flammable gas, a gas under pressure, acute inhalation toxicity, and target-organ toxicity, but classifications differ between suppliers and regions. One correction worth making: arsine should not be described as a “Category 1 pyrophoric gas” unless the SDS in front of you says so. Arsine is flammable, and that is a different classification. 

Section 7: Handling and storage 

Look for storage conditions, incompatible materials, handling precautions, and cylinder requirements such as securing, ventilation, and separation. 

Section 8: Exposure controls and PPE 

This section lists applicable exposure limits, recommended engineering controls, PPE, and respiratory protection information. Compare the limits it quotes with current regulatory sources. 

Section 10: Stability and reactivity 

Review reactivity, incompatible materials, conditions to avoid, and hazardous decomposition products. 

Section 11: Toxicological information 

Use it to confirm routes of exposure, acute toxicity data, delayed health effects, and target organs. 

Keeping these sections current across dozens of chemicals is easier with a managed system; see SDS Management Software (placeholder URL and anchor text, replace with the specified ones). 

Frequently asked questions 

• What is the OSHA exposure limit for arsine? 

OSHA's permissible exposure limit for arsine is 0.05 ppm (0.2 mg/m³) averaged over an 8-hour workday, listed in 29 CFR 1910.1000, Table Z-1. It is the enforceable U.S. limit. NIOSH and ACGIH publish their own values, but those are recommendations or guidelines, not law. 

• Can you smell arsine gas before it becomes dangerous? 

No. Arsine can smell like garlic, but this is usually noticed only above the OSHA PEL. Sensitivity varies, and olfactory fatigue can dull the sense further. A lack of odor proves nothing, so workplaces should rely on calibrated gas detectors and not on smell. 

• How long after arsine exposure do symptoms appear? 

Symptoms can be delayed, and a worker may feel normal at first. Serious effects such as red blood cell destruction and kidney injury can emerge later. Because timing varies, anyone with suspected exposure should receive immediate medical evaluation and not wait for symptoms to develop. 

• Is arsine flammable or pyrophoric? 

Arsine is classified as a flammable gas. It is not generally described as a pyrophoric gas, so earlier statements calling it a Category 1 pyrophoric gas should be corrected. Always confirm the classification on the current supplier SDS, since classifications can vary slightly between suppliers. 

• Where is arsine gas produced accidentally? 

Arsine can form when arsenic-containing materials such as ores, slags, dross, and scrap contact acid or moisture. It is most often a concern in smelting, refining, metal recycling, acid cleaning, and maintenance work on equipment that has handled arsenic-bearing material. 

Conclusion 

Arsine earns its reputation: it is invisible, it can be harmful before anyone smells it, and its worst effects may show up hours after the worker has walked away feeling fine. That combination is why programs built on awareness alone tend to fail, and why programs built on layers tend to hold. 

The practical takeaways are short. Know where arsine is used and where it could be generated by accident, especially in operations that combine arsenic-bearing material with acid or moisture. Treat the OSHA PEL of 0.05 ppm (8-hour TWA) as the legal floor, and keep NIOSH and ACGIH values in their proper role as recommendations and guidelines. Detect with instruments, never with a nose. Put the effort into engineering controls first, back them with clear procedures and training, and keep respiratory protection as the last barrier and not the first. 

Finally, keep the SDS current and in the hands of the people who need it, including responding medical staff. Any suspected exposure is a medical emergency, and the time to decide who calls, who evacuates, and who stays out is long before a cylinder is changed. 

References 

• https://www.cdc.gov/niosh/npg/npgd0040.html 

• https://www.osha.gov/chemicaldata/660 

• https://osha.prod.pace.dol.gov/laws-regs/regulations/standardnumber/1910/1910.1000TABLEZ1 

• https://www.law.cornell.edu/cfr/text/29/1910.1000 

• https://cdc.gov/niosh/ershdb/emergencyresponsecard_29750014.html 

• https://nrt.org/sites/2/files/Arsine%20SA%20QRG%20FINAL%202017%2004%2025.pdf 

• https://cameochemicals.noaa.gov/report?key=CH178 

• https://www.gov.uk/government/publications/arsenic-hydride-properties-incident-management-and-toxicology/arsine-and-stibine-toxicological-overview 

• https://www.epa.gov/sites/default/files/2021-04/documents/arsenic_april_2021.pdf 

• https://www.nature.com/articles/3780012.pdf 

• https://publications.iarc.who.int/120 

• https://www.ncbi.nlm.nih.gov/books/NBK304375/ 

• https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134 

• https://www.osha.gov/training/library/respiratory-protection/major-requirements