No metadata available
Chemical Identity
CAS Number
74-90-8
Formula
HCN
Molecular Weight
27.03 g/mol
Exposure Limits Comparison
Health Effects
Cellular Asphyxiation
Yes
Rapid Unconsciousness
Yes
Respiratory Failure
Yes
Fatal At High Dose
Yes
Todd DunningMAUnited States
Optical Materials for Laser SystemsPublished
Jan 6, 2026
Hydrogen Cyanide Compound
Hydrogen Cyanide Compound safety information for laser cleaning. Health hazards, exposure limits, and protective equipment requirements.
Chemical Properties
Detection Monitoring
- SensorTypes
- Electrochemical
- Semiconductor
- Photoionization detector (PID)
- Infrared
- DetectionRange
- 0-30 ppm typical (must detect sub-ppm levels)
- AlarmSetpoints
- Low
- 4.7 ppm (NIOSH ceiling)
- High
- 10 ppm (OSHA ceiling)
- Evacuate
- 50 ppm (NIOSH IDLH) - IMMEDIATELY LIFE-THREATENING
- ColorimetricTubes
- Dräger CH29901
- Gastec 12L/12
- Kitagawa 710
- AnalyticalMethods
Method Technique DetectionLimit NIOSH 6010 Spectrophotometry (colorimetric) 0.2 ppb OSHA PV2074 Ion chromatography 0.03 ppm - OdorThreshold
- UNRELIABLE - 20-40% of population cannot smell HCN (genetic). Odor threshold (0.58-5 ppm) overlaps toxic range. NEVER rely on odor - MANDATORY continuous monitoring with alarms.
Environmental Impact
- AquaticToxicity
- Extremely toxic to aquatic life. LC50 (fish, 96h): 0.05-0.3 mg/L. Toxic at parts-per-billion levels.
- Biodegradability
- Readily biodegradable by specialized bacteria. Oxidizes to carbon dioxide and ammonia. Half-life in water: hours to days.
- Bioaccumulation
- Does not bioaccumulate. Log Kow: 0.66. Rapidly metabolized or volatilizes.
- SoilMobility
- High mobility in soil. Volatilizes rapidly. Does not adsorb to soil.
- AtmosphericFate
- Rapidly oxidizes via hydroxyl radicals. Atmospheric half-life: 1-3 years. Photolyzes in sunlight.
- OzoneDepletion
- false
- ReportableReleases
- Water
- 10 lbs (4.54 kg) to navigable waters - IMMEDIATELY reportable
- Air
- 10 lbs/day (CERCLA RQ) - ANY release must be reported immediately due to extreme toxicity
Ppe Requirements
- Respiratory
- MANDATORY: Full-face pressure-demand SCBA or positive-pressure supplied-air respirator with escape SCBA. No air-purifying respirators approved - extremely toxic.
- Eye Protection
- Chemical safety goggles and full face shield. Liquid contact causes severe burns.
- Skin Protection
- Butyl rubber gloves (>0.5mm), nitrile gloves, fully-encapsulating chemical protective suit. HCN absorbs rapidly through skin.
Reactivity
- Stability
- UNSTABLE. Polymerizes violently when contaminated with water, bases, or ammonia. Must be stabilized with acid.
- Polymerization
- May polymerize explosively if not stabilized. Polymerization exothermic - can rupture containers and cause explosions.
- IncompatibleMaterials
- Water (polymerization)
- Strong bases (sodium hydroxide)
- Acids (releases HCN gas)
- Oxidizers
- Ammonia
- Amines
- Sulfur
- Acetaldehyde
- Halogens
- HazardousDecomposition
- Nitrogen oxides (NOx)
- Hydrogen cyanide gas
- Carbon monoxide
- Ammonia
- ConditionsToAvoid
- Heat
- Moisture/water
- Alkaline conditions
- Light
- Flames
- Sparks
- Oxidizers
- Contamination of any kind
- ReactivityHazard
- EXTREMELY REACTIVE. Violent polymerization with alkaline materials. Reacts with oxidizers causing fire and explosion. Attacks some metals (copper, zinc) forming explosive metal cyanides.
Regulatory Classification
- UnNumber
- UN1051 (anhydrous, stabilized), UN1613 (solution)
- DotHazardClass
- 6.1 (Toxic), 3 (Flammable liquid)
- DotLabel
- Poison, Flammable Liquid
- NfpaCodes
- Health
- 4
- Flammability
- 4
- Reactivity
- 2
- Instability
- 2
- EpaHazardCategories
- Acute toxicity (fatal if inhaled/swallowed/skin contact)
- Flammability
- Skin corrosion
- Serious eye damage
- SaraTitleIii
- true
- CerclaRq
- 10 pounds (4.54 kg)
- RcraCode
- P063
Contaminants That Produce Hydrogen Cyanide
Hydrogen Cyanide is produced as a gaseous or particulate byproduct during laser ablation of contaminated surfaces. The generation rate and chemical form depend on the source contaminant and substrate combination. Proper exhaust ventilation and gas monitoring ensure safe working concentrations in laser cleaning enclosures.
Chemical Properties
Molecular formula, CAS number, molecular weight, and chemical structure
- Type
- chemical_properties
- Id
- hydrogen-cyanide-physical-data
Physical Properties
Chemical and physical characteristics
- BoilingPoint
- 25.6°C (78°F)
- MeltingPoint
- -13.3°C (8°F)
- VaporPressure
- 620 mmHg @ 20°C
- VaporDensity
- 0.94 (Air=1)
- SpecificGravity
- 0.687 @ 20°C (liquid)
- FlashPoint
- -17.8°C (0°F) closed cup
- AutoignitionTemp
- 538°C (1000°F)
- ExplosiveLimits
- LEL: 5.6%, UEL: 40%
- Appearance
- Colorless or pale blue liquid, colorless gas
- Odor
- Faint bitter almond odor; WARNING: 20-40% of population cannot detect odor (genetic variation)
Alternative Names
Synonyms and chemical identifiers
- Synonyms
- Hydrocyanic acid
- Prussic acid
- Formonitrile
- Methanenitrile
- Carbon hydride nitride
- HCN
- CommonTradeNames
- Zyklon
- Cyclone B (historical)
- OtherIdentifiers
- RtecsNumberMW6825000EcNumber200-821-6PubchemCid768
Health Effects
Adverse health impacts from exposure to this compound
- Route
- inhalation
- Effect
- Rapid onset of headache, dizziness, nausea, confusion, seizures, respiratory failure, and cardiovascular collapse due to cellular hypoxia
- Severity
- severe
- Onset
- immediate
- Route
- skin_contact
- Effect
- Systemic absorption leading to cyanosis, weakness, hyperventilation, coma, and potential death; liquid form causes burns
- Severity
- severe
- Onset
- short-term
- Route
- eye_contact
- Effect
- Severe irritation, pain, lacrimation, blurred vision, and possible corneal injury
- Severity
- high
- Onset
- immediate
- Route
- ingestion
- Effect
- Burning sensation in mouth and throat, nausea, vomiting, abdominal pain, and rapid systemic toxicity including convulsions and death
- Severity
- severe
- Onset
- immediate
Personal Protective Equipment
Required safety equipment for handling this compound
- Respiratory
- MANDATORY: Full-face pressure-demand SCBA or positive-pressure supplied-air respirator with escape SCBA. No air-purifying respirators approved - extremely toxic.
- Skin
- Butyl rubber gloves (>0.5mm), nitrile gloves, fully-encapsulating chemical protective suit. HCN absorbs rapidly through skin.
- Eye
- Chemical safety goggles and full face shield. Liquid contact causes severe burns.
- MinimumLevel
- Level A for unknown concentrations or >10 ppm, Level B minimum for known concentrations <10 ppm
- SpecialNotes
- HCN penetrates ordinary clothing. Rapidly absorbed through skin causing systemic poisoning. Use butyl rubber - NOT neoprene or natural rubber. Emergency cyanide antidote kit must be immediately available.
Exposure Limits
OSHA, NIOSH, and ACGIH exposure thresholds
- OshaPelPpm
- 10
- OshaPelMgM3
- 11
- NioshRelMgM3
- 5
- AcgihTlvMgM3
- 4.7
- WorkplaceExposure
- OshaPeltwa8Hr: nullstel15Min: nullceiling: 10 ppmNioshReltwa8Hr: 4.7 ppmstel15Min: 4.7 ppmceiling: nullidlh: 50 ppmAcgihTlvtwa8Hr: 10 ppmstel15Min: 15 ppmceiling: nullBiologicalExposureIndices0: [object Object]1: [object Object]
Storage Requirements
Safe storage conditions and compatibility
- TemperatureRange
- Store below 25°C (77°F), ideally <15°C. Avoid heating above boiling point.
- Ventilation
- Outdoor storage strongly preferred. If indoors: continuous mechanical ventilation with emergency backup, HCN gas detection with evacuation alarms
- Incompatibilities
- Acids
- Strong bases
- Oxidizers
- Water (polymerization catalyst)
- Ammonia
- Sulfur
- Halogens
- Amines
- ContainerMaterial
- Stainless steel or glass with PTFE-lined caps. Stabilized with acid (H3PO4 or H2SO4) to prevent polymerization. Never use copper, copper alloys, or iron containers.
- Segregation
- Isolated storage area, separate from all other chemicals. Secure area with restricted access. Post "POISON GAS - AUTHORIZED PERSONNEL ONLY" signs.
- QuantityLimits
- Minimize quantities stored. Per OSHA, treat as extremely hazardous. Many facilities limit to <5 gallons on-site.
- SpecialRequirements
- CRITICAL: Store with stabilizer (acid). Check stabilizer level regularly. Refrigerated storage recommended. Gas detection system MANDATORY. Emergency shower/eyewash within 10 seconds travel. Cyanide antidote kits at storage location. Written emergency procedures posted.
Emergency Response
Procedures for spills, exposure, and incidents
- FireHazard
- Extremely flammable liquid and vapor. Wide explosive range. May polymerize explosively if contaminated. Vapors may travel to ignition source.
- FireSuppression
- Evacuate area immediately - extremely toxic combustion products. Use unmanned hose holders or monitor nozzles. Dry chemical, CO2, alcohol-resistant foam from safe distance. Water spray to cool cylinders.
- SpillProcedures
- EVACUATE IMMEDIATELY - call HAZMAT team. Self-Contained Breathing Apparatus MANDATORY. Eliminate ignition sources. Contain with sand/vermiculite. Neutralize with sodium hydroxide or calcium hypochlorite solution. Decontaminate area thoroughly.
- ExposureImmediateActions
- MEDICAL EMERGENCY - minutes count. Remove to fresh air immediately. Administer 100% oxygen. Apply cyanide antidote kit (amyl nitrite, sodium nitrite, sodium thiosulfate) per protocol. CPR if needed. Rush to hospital - inform medical staff of cyanide exposure immediately.
- EnvironmentalHazards
- Extremely toxic to all life. Highly volatile - rapidly disperses but lethal during dispersion. Report any release immediately. Toxic to aquatic life at extremely low concentrations.
- SpecialHazards
- ONE OF THE MOST TOXIC INDUSTRIAL CHEMICALS. Inhibits cellular respiration by binding to cytochrome oxidase. Death can occur within minutes. Polymerizes violently with alkaline contamination. Decomposes producing nitrogen oxides and hydrogen cyanide gas.
Regulatory Classification
DOT, UN, and NFPA hazard classifications
- UnNumber
- UN1051 (anhydrous, stabilized), UN1613 (solution)
- DotHazardClass
- 6.1 (Toxic), 3 (Flammable liquid)
- DotLabel
- Poison, Flammable Liquid
- NfpaCodes
- Health4Flammability4Reactivity2SpecialnullInstability2
- EpaHazardCategories
- Acute toxicity (fatal if inhaled/swallowed/skin contact)
- Flammability
- Skin corrosion
- Serious eye damage
- SaraTitleIii
- true
- CerclaRq
- 10 pounds (4.54 kg)
- RcraCode
- P063
Environmental Impact
Toxicity, biodegradability, and environmental fate
- AquaticToxicity
- Extremely toxic to aquatic life. LC50 (fish, 96h): 0.05-0.3 mg/L. Toxic at parts-per-billion levels.
- Biodegradability
- Readily biodegradable by specialized bacteria. Oxidizes to carbon dioxide and ammonia. Half-life in water: hours to days.
- Bioaccumulation
- Does not bioaccumulate. Log Kow: 0.66. Rapidly metabolized or volatilizes.
- SoilMobility
- High mobility in soil. Volatilizes rapidly. Does not adsorb to soil.
- AtmosphericFate
- Rapidly oxidizes via hydroxyl radicals. Atmospheric half-life: 1-3 years. Photolyzes in sunlight.
- OzoneDepletion
- false
- ReportableReleases
- Water10 lbs (4.54 kg) to navigable waters - IMMEDIATELY reportableAir10 lbs/day (CERCLA RQ) - ANY release must be reported immediately due to extreme toxicity
FAQ
Common Questions and Answers
What personal protective equipment (PPE) should I wear to minimize hydrogen cyanide (HCN) exposure risks during laser cleaning of metal surfaces?
- Use a full-facepiece respirator with cartridges specifically rated for HCN or acid gases, combined with chemical-resistant gloves, boots, and a full-body suit made from materials like butyl rubber to block rapid skin absorption. Ensure the workspace has adequate ventilation or local exhaust systems to reduce inhalation hazards, and always perform air monitoring with HCN-specific detectors to keep exposures below the OSHA ceiling limit of 10 ppm. If HCN levels approach the limit, immediately evacuate and decontaminate any exposed skin with a dilute sodium hypochlorite solution followed by thorough rinsing.
Detection & Monitoring
Methods for detecting and measuring this compound
- SensorTypes
- Electrochemical
- Semiconductor
- Photoionization detector (PID)
- Infrared
- DetectionRange
- 0-30 ppm typical (must detect sub-ppm levels)
- AlarmSetpoints
- Low4.7 ppm (NIOSH ceiling)High10 ppm (OSHA ceiling)Evacuate50 ppm (NIOSH IDLH) - IMMEDIATELY LIFE-THREATENING
- ColorimetricTubes
- Dräger CH29901
- Gastec 12L/12
- Kitagawa 710
- AnalyticalMethods
- [object Object]
- [object Object]
- OdorThreshold
- UNRELIABLE - 20-40% of population cannot smell HCN (genetic). Odor threshold (0.58-5 ppm) overlaps toxic range. NEVER rely on odor - MANDATORY continuous monitoring with alarms.
Reactivity
Chemical reactivity and incompatibilities
- Stability
- UNSTABLE. Polymerizes violently when contaminated with water, bases, or ammonia. Must be stabilized with acid.
- Polymerization
- May polymerize explosively if not stabilized. Polymerization exothermic - can rupture containers and cause explosions.
- IncompatibleMaterials
- Water (polymerization)
- Strong bases (sodium hydroxide)
- Acids (releases HCN gas)
- Oxidizers
- Ammonia
- Amines
- Sulfur
- Acetaldehyde
- Halogens
- HazardousDecomposition
- Nitrogen oxides (NOx)
- Hydrogen cyanide gas
- Carbon monoxide
- Ammonia
- ConditionsToAvoid
- Heat
- Moisture/water
- Alkaline conditions
- Light
- Flames
- Sparks
- Oxidizers
- Contamination of any kind
- ReactivityHazard
- EXTREMELY REACTIVE. Violent polymerization with alkaline materials. Reacts with oxidizers causing fire and explosion. Attacks some metals (copper, zinc) forming explosive metal cyanides.
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