Epichlorohydrin (C₃H₅ClO)
Epichlorohydrin is a reactive chlorinated epoxide used mainly in epoxy-resin, glycerol and specialty chemical production. It can be absorbed through skin, is a potential occupational carcinogen and can polymerize under incompatible conditions. A complete program combines closed handling, dermal protection, low-level vapor measurement and fire protection.
What Is Epichlorohydrin?
Epichlorohydrin is a reactive chlorinated epoxide used mainly in epoxy-resin, glycerol and specialty chemical production. It can be absorbed through skin, is a potential occupational carcinogen and can polymerize under incompatible conditions. A complete program combines closed handling, dermal protection, low-level vapor measurement and fire protection.
Core references used for this page: NIOSH Pocket Guide — Epichlorohydrin; NIST Chemistry WebBook — Epichlorohydrin; OSHA 1910.1000 — Air Contaminants.
Epichlorohydrin at a Glance
Appearance and fire behavior
Colorless liquid with a slightly irritating, chloroform-like odor
Flammable liquid and vapor; NIOSH lists a typical LEL of 3.8% and UEL of 21%.
Exposure-limit context
NIOSH treats epichlorohydrin as a potential occupational carcinogen. OSHA PEL: 5 ppm TWA with skin notation. NIOSH IDLH: carcinogen notation at 75 ppm.
Properties That Affect Safety and Measurement
| Property | Value or description | Engineering significance |
|---|---|---|
| Formula | C3H5ClO | Identifies the target gas or atmospheric parameter. |
| CAS number | 106-89-8 | Useful for chemical records, SDS review and analytical methods. |
| Molecular weight | 92.52 g/mol | Supports engineering calculations but is not a complete detector-placement rule. |
| Boiling / phase behavior | About 116.5°C (242°F) | Important for cryogenic releases, frostbite and pressure control. |
| Relative gas density | Vapor about 3.2 times heavier than air | One dispersion input among release momentum, temperature, ventilation and geometry. |
| Appearance and odor | Colorless liquid with a slightly irritating, chloroform-like odor | Human senses cannot provide a quantified or automatic safety response. |
| Fire behavior | Flammable liquid and vapor; NIOSH lists a typical LEL of 3.8% and UEL of 21%. | Determines whether enrichment, oxidizing behavior or nonflammability must be addressed. |
| Exposure / threshold context | NIOSH treats epichlorohydrin as a potential occupational carcinogen. OSHA PEL: 5 ppm TWA with skin notation. NIOSH IDLH: carcinogen notation at 75 ppm. | Do not treat occupational limits, oxygen boundaries and alarm settings as interchangeable. |
Gas density alone is not sufficient to determine detector placement. Release point, gas temperature, process pressure, ventilation, air movement, room geometry, obstructions and worker location must all be considered.
Where Epichlorohydrin Is Used or Released
Common sources and release points
- Epoxy-resin and glycidyl-ether manufacturing
- Synthetic glycerol and wet-strength resin production
- Chemical reactors, distillation and storage
- Tank, drum and transfer connections
- Sampling, maintenance and vessel entry
- Waste and contaminated-water treatment
Industries and applications
Applications determine whether the measurement objective is personnel protection, process control, purity, emissions management or leak location.
- Epoxy resins
- Glycidyl ethers
- Wet-strength resins
- Synthetic glycerol
- Elastomers and specialty polymers
- Chemical intermediate
Epoxy resins
Review storage, transfer, process equipment, ventilation, occupied access and maintenance states for credible releases.
Glycidyl ethers
Review storage, transfer, process equipment, ventilation, occupied access and maintenance states for credible releases.
Wet-strength resins
Review storage, transfer, process equipment, ventilation, occupied access and maintenance states for credible releases.
Synthetic glycerol
Review storage, transfer, process equipment, ventilation, occupied access and maintenance states for credible releases.
Elastomers and specialty polymers
Review storage, transfer, process equipment, ventilation, occupied access and maintenance states for credible releases.
Chemical intermediate
Review storage, transfer, process equipment, ventilation, occupied access and maintenance states for credible releases.
Understand How Vapor Exposure Develops
Evaporation or process release
Epichlorohydrin vapor can arise from open containers, coating, cleaning, transfer, reaction, drying, waste or leaking equipment.
Worker exposure
Breathing-zone concentration depends on emission rate, task duration, local exhaust, room air movement and proximity to the source.
Fire or chronic-health pathway
A vapor may create an acute flammability hazard at high concentration while much lower concentrations can still matter for occupational exposure.
Measurement response
Broad VOC screening, compound-specific exposure measurement and %LEL protection answer different questions and may require different instruments.
Primary Hazards of Epichlorohydrin
People and atmosphere
- Potential occupational carcinogenicity
- Skin absorption and deep painful skin injury
- Eye and respiratory irritation
- Liver, kidney and reproductive-system concerns
- Flammable vapor
- Polymerization with acids, bases or heat
Reactivity, materials and equipment
- Keep away from strong acids, bases, oxidizers, reactive metals and water under uncontrolled conditions.
- Verify glove and clothing breakthrough data because skin notation is important.
- Control contamination and temperature in storage and process systems.
- Use closed sampling and local exhaust where feasible.
Never enter an unknown atmosphere. Leave the affected area, contact trained emergency responders, use appropriate respiratory protection and follow the facility emergency plan.
Separate Exposure Limits, Alarm Settings and Instrument Ranges
NIOSH treats epichlorohydrin as a potential occupational carcinogen. OSHA PEL: 5 ppm TWA with skin notation. NIOSH IDLH: carcinogen notation at 75 ppm.
Compound-specific ppm
Used for occupational exposure or process concentration. TWA, STEL, ceiling and IDLH values have different time bases and regulatory meanings.
TVOC / PID screening
A broad-response value can reveal change or locate a source, but it does not identify the compound and depends on lamp, correction factor and mixture.
Alarm programming
Alarm settings depend on the gas, application, jurisdiction, instrument, applicable standards and site-specific risk assessment.
Define the Safety Function Before Selecting a Sensor
Questions to answer
- What containers, coatings, cleaners, tanks or processes can release the vapor?
- Is the objective compound-specific exposure, TVOC screening, process analysis or %LEL protection?
- What ranges, response times and environmental limits apply?
- Which alarms control ventilation, isolation, evacuation or process action?
- How will the complete system be bump tested, calibrated and documented?
Instrument terms are not interchangeable
- Gas sensor: the sensing element.
- Gas detector: sensor plus electronics, output and alarm functions.
- Gas monitor: continuous or portable instrument that may log or calculate exposure.
- Gas analyzer: measures composition, purity or process concentration.
- Leak detector: locates or indicates leakage and may not report area concentration.
How Epichlorohydrin Is Measured
Photoionization detector
A UV lamp ionizes detectable epichlorohydrin and other VOCs.
Compound-specific infrared / FTIR
Infrared absorption is measured in a controlled cell.
Gas chromatography / validated sampling
Samples are separated and quantified compound specifically.
Combustible-gas detector
Catalytic or optical detection reports concentrated vapor as %LEL.
Where Monitoring Points Should Be Installed
Priority locations
- At credible release points such as cylinder connections, valves, regulators, pumps, seals, transfer couplings and process enclosures
- Inside or immediately outside exhausted cabinets, tool enclosures or local exhaust zones when the release can be contained there
- At representative occupied locations and worker breathing zones when personnel exposure is the measurement objective
- At ventilation dead zones, pits, trenches, mezzanines or ceiling pockets identified by airflow and release analysis
- At confined-space entry points and inside the space under the approved atmospheric-testing procedure
- Where maintenance access is practical so bump testing, calibration and sensor replacement can be completed safely
Placement review checklist
- Release point and failure mode
- Gas temperature, pressure and jet direction
- Normal, standby and failed ventilation states
- Room geometry, pits, ceilings and connected voids
- Worker breathing zones, exits and rescue approach
- Sampling delay and maintenance access
Validate detector coverage against real operating modes. A high or low mounting rule based only on molecular weight is not an adequate design method.
Prove the Complete Monitoring System Works
Functional verification
- Inspect power, enclosure, inlet, filter, wiring and fault status.
- Apply the correct challenge gas or reference atmosphere.
- Confirm response, display, local alarm, relays and remote notification.
- Calibrate when required or when the functional check fails.
- Record results, sensor age, faults and corrective action.
When additional testing is needed
- After over-range exposure or a high-concentration solvent release
- After condensation, washdown, filter loading or solvent contamination
- After repair, relocation, power loss or ventilation changes
- After unexplained drift, failed alarms or pump-flow faults
- Before critical confined-space or emergency work
Control Releases Before Relying on Alarms
Engineering controls
- Leak-tight piping, compatible materials and suitable pressure relief
- Ventilation sized for credible normal and abnormal releases
- Remote isolation, shutdown and safe discharge routing
- Alarm interlocks that are tested as a complete cause-and-effect system
- Confined-space, hazardous-location, hot-work and chemical-handling procedures as applicable
Gas-specific emergency priorities
- Warn personnel and evacuate or isolate the affected area according to the site emergency plan.
- Do not enter an unknown or oxygen-deficient atmosphere without trained responders and suitable atmosphere-supplying respiratory protection.
- Shut off the source remotely when this can be done without exposing personnel.
- Maintain or increase engineered exhaust only when the system is designed for the chemical and release condition.
- Confirm the target gas, oxygen, flammability and relevant by-products before re-entry or return to service.
Common Causes of Delayed or Misleading Readings
Sampling system considerations
- Use NIOSH 1010 or another validated method for occupational assessment.
- Include dermal exposure in the risk assessment.
- Verify PID response rather than assuming a strong signal.
- Prevent condensation and sample loss in long lines.
Environmental and cross-sensitivity review
Verify PID lamp energy, response factors, background VOCs, oxygen dependency, pressure, temperature, humidity, condensation, response time, sensor aging and cross-sensitivity. The complete installed instrument—not only the bare sensor—must meet the required safety function.
Practical Answers to Frequent Mistakes
Air monitoring captures all exposure.
Skin absorption can be significant.
A standard PID always detects epichlorohydrin well.
Lamp energy and response must be demonstrated.
Non-visible vapor means no hazard.
Relevant concentrations are invisible.
LEL monitoring addresses cancer risk.
Low-level exposure control is a separate objective.
Comparing Measurement Approaches
| Technology | Suitable use | Advantages | Limitations |
|---|---|---|---|
| Photoionization detector | Leak screening and task surveys with a validated response factor. | Fast and portable. | The ionization potential is close to common lamp energy and response can be weak or variable; field validation is essential. |
| Compound-specific infrared / FTIR | Fixed extractive monitoring, process analysis and exhaust investigation. | Potentially selective continuous measurement. | Water and other chlorinated or oxygenated compounds can interfere. |
| Gas chromatography / validated sampling | Occupational exposure and mixed-process air. | High specificity. | Not an immediate alarm and skin exposure remains outside the air result. |
| Combustible-gas detector | Fire and explosion protection. | Rapid high-level alarm. | Cannot replace low-level carcinogen and skin-exposure control. |
Epichlorohydrin FAQ
What does epichlorohydrin smell like?
Odor descriptions and odor thresholds vary. Smell is not a quantified measurement and must not be the primary warning method.
Is epichlorohydrin flammable?
Flammable liquid and vapor; NIOSH lists a typical LEL of 3.8% and UEL of 21%. Review the current SDS and actual process conditions.
Is epichlorohydrin heavier than air?
Vapor about 3.2 times heavier than air Density alone is not sufficient to determine detector placement.
What sensor detects epichlorohydrin?
The correct technology depends on the required concentration range, selectivity, response time, background gases, humidity, pressure and whether the objective is exposure, leak, process or fire protection.
Where should epichlorohydrin detectors be installed?
Start with the release point, airflow, enclosure design, occupied zones and required response time. Validate placement through commissioning or a dispersion assessment where necessary.
What measuring range is suitable for epichlorohydrin?
Choose the range around the applicable exposure criterion, process concentration, credible release and required resolution. ppm, vol% and %LEL ranges serve different functions.
Can a portable multi-gas detector measure epichlorohydrin?
Only when it has a compatible sensor and validated range. A standard four-gas instrument should not be assumed to identify every specialty gas or vapor.
How often should a detector be calibrated?
Follow the manufacturer, applicable regulation, site risk assessment and sensor history. Bump testing verifies response; calibration adjusts accuracy.
Can one detector cover all release scenarios?
Usually not. Source monitoring, room monitoring, worker exposure and process analysis may require different ranges, locations or technologies.
What should be done during a leak?
Leave the area, prevent unprotected entry, notify trained responders and isolate remotely when safe. Follow the current emergency plan and SDS.
Sources and Further Reading
Requirements and numerical values may differ by jurisdiction, standard, pressure, altitude, composition and test condition. Use the original sources and applicable local rules when designing a system.
- NIOSH Pocket Guide — Epichlorohydrin
- NIST Chemistry WebBook — Epichlorohydrin
- OSHA 1910.1000 — Air Contaminants
- OSHA 1910.134 — Respiratory Protection
- PubChem — Epichlorohydrin
Educational content only: This page does not replace emergency services, medical advice, a workplace risk assessment, applicable codes, manufacturer instructions or qualified engineering judgement.
Plan an Epichlorohydrin Monitoring System
Share the source, target concentration, background gases, temperature, humidity, ventilation, required response time, certifications, alarm actions and maintenance constraints.