1,3-Butadiene technical guidelines

1,3-Butadiene (BD) is a colorless, flammable gas with a mildly aromatic odor and a liquid form when compressed; its boiling point is −4.7 °C (23.5 °F), vapor density is about 1.87 (air = 1 at BD boiling point), specific gravity is 0.62 at 20 °C, and vapor pressure at 20 °C is about 910 mm Hg.

• These values come from the Substance Technical Guidelines for 1,3-Butadiene (Appendix B to 1910.1051), which you should use when assessing storage, ventilation, and emergency response planning.
• The low boiling point and high vapor pressure mean BD readily becomes a gas at room temperature, increasing inhalation and flammability risks.

Yes. For OSHA purposes, 1,3-Butadiene is classified as a flammable gas and must be handled under flammable-gas storage requirements.

• The Appendix B technical guidelines for 1,3-Butadiene explicitly state BD is a flammable gas for compliance with 29 CFR 1910.106.
• That classification affects how you store and separate BD from ignition sources and other incompatible materials under the flammable liquids/gases rules.

1,3-Butadiene has lower and upper flammable limits in air of about 2.0% and 11.5% by volume, respectively, and these limits determine the concentration range in which BD can ignite.

• The Appendix B guidelines provide these flammable limits and note that even concentrations well below the lower limit (for example, 7,500 ppm) can pose a fire/explosion hazard in certain circumstances.
• Use these limits to evaluate explosion risk, to set ventilation rates, and to plan gas detection and alarm systems.

Fight 1,3-Butadiene fires from a protected location or maximum possible distance, stop the flow of gas before extinguishing, use CO2 for small fires and polymer or alcohol foams for large fires, and cool fire-exposed cylinders with water spray.

• These procedures are summarized in the Appendix B guidelines for 1,3-Butadiene.
• Because BD vapors are heavier than air and can flash back, ensure responders eliminate ignition sources in the area and maintain safe separation distances when possible.

Immediately eliminate ignition sources, ventilate the area, restrict unprotected personnel from the area, stop or control the leak if it can be done safely, and for leaking cylinders remove the cylinder to a safe place to repair or let it empty if it cannot be fixed in place.

• These steps come directly from the Appendix B spill, leak, and disposal procedures for 1,3-Butadiene.
• Remember: BD is highly flammable and vapors can travel to distant ignition sources; use appropriate PPE and only allow trained personnel into the area until cleanup is complete.

Discarded or disposed 1,3-Butadiene is an EPA-listed hazardous waste (ignitability, D001) and must be managed and disposed of in compliance with federal hazardous waste regulations and only at permitted facilities.

• The Appendix B guidelines explain that BD waste must meet the EPA requirements in 40 CFR part 261 and related parts, and employers should also check state and local rules which can be more restrictive.
• Ensure transportation, treatment, and disposal are performed by permitted handlers and facilities and maintain required waste manifests and records as applicable.

Monitoring frequency depends on the exposure scenario: annual 8‑hr TWA monitoring is required when only the action level is exceeded, periodic monitoring is required when the 8‑hr TWA or STEL are exceeded, and STEL monitoring is required where the STEL may be exceeded — follow the monitoring frequencies and Table 1 in the standard.

• See the monitoring frequency rules and Table 1 in 1910.1051AppB that explain scenario-based monitoring together with the monitoring procedures in 1910.1051(d)(3)(ii) and 1910.1051(d)(3)(iii).
• The employer may reduce monitoring frequency to annual when at least two consecutive measurements, taken at least 7 days apart, show exposures below the 8‑hr TWA but at or above the action level (see the Table 1 notes in the Appendix).

Use validated sampling and analysis methods described in Appendix D of the standard; the employer must select a method that meets the accuracy and precision requirements of the standard for their field conditions.

• Appendix B points to Appendix D for the OSHA-tested, validated methods for BD sampling and analysis.
• The chosen method must achieve the standard's required accuracy at the relevant concentration levels (see the next Q&A about accuracy).

The monitoring method must be accurate with 95% confidence to ±25% for BD concentrations at or above 1 ppm, and to ±35% for concentrations below 1 ppm.

• This accuracy requirement is stated in the Appendix B monitoring techniques guidance.
• Choose laboratory and field methods (from Appendix D) that provide documented performance meeting those criteria.

Air samples must be taken in the employee's breathing zone so the results reflect what the employee is actually inhaling.

• The Appendix B guidance specifically says full-shift measurements should be consecutive samples covering the full shift and be taken in the breathing zone.
• For STEL sampling, samples must represent 15-minute exposures associated with operations most likely to exceed the STEL on each job and shift (see 1910.1051(d)).

No — while BD has a reported odor threshold around 0.45 ppm and many workers may smell it before overexposure, odor should not be relied on as a detection or warning system for hazardous exposures.

• The Appendix B evaluation of warning properties notes the odor threshold is about half of the 1 ppm PEL and well below the 5 ppm STEL, but odor perception varies and cannot replace monitoring or detection equipment.
• Use continuous or periodic monitoring, gas detectors, and appropriate respiratory protection procedures instead of relying on smell alone.

Employees should be provided and required to use impervious clothing, gloves, and at least an eight‑inch face shield (plus other protective clothing) to prevent the skin from freezing if they contact liquid BD, and splash-proof safety goggles when liquid exposure to the eyes is possible.

• These PPE recommendations are in the Appendix B guidance for 1,3-Butadiene, and general workplace hygiene and washing facility requirements are addressed under 1910.141.
• Ensure PPE selection considers compatibility with BD, training in use, and procedures for decontamination or disposal of contaminated PPE.

Any clothing wet with liquid BD should be removed immediately and not re-worn until the butadiene has evaporated.

• This instruction appears in the Appendix B guidance to prevent prolonged skin contact and potential freezing injuries from the cryogenic effect of the liquid.
• Provide changing areas, disposal or laundering procedures, and training so employees can remove and manage contaminated clothing safely.

Where liquid BD may contact the eyes, employees should be provided with and required to use splash-proof safety goggles.

• The Appendix B guidance specifies splash-proof goggles for liquid-exposure situations.
• Combine goggles with face shields when splashes are likely to protect the whole face, and ensure eyewash/flush stations are available per general hygiene requirements (1910.141).

Employers should keep workplaces clean and provide adequate washing facilities with hot and cold water maintained in sanitary condition; they must also emphasize removal of contaminated clothing and access to emergency washing where liquid BD exposure is possible.

• The Appendix B guidance specifically references hygiene and links it to the general sanitation standard at 1910.141.
• Ensure policies, training, and facilities (showsers/eyewash, laundering, clean break areas) are present and maintained.

Store BD in tightly closed containers in a cool, well-ventilated area, use non-sparking tools, effectively ground metal containers, and follow flammable gas storage rules to avoid explosion hazards.

• The Appendix B precautions recommend grounding, non-sparking tools, and cool ventilated storage; these measures align with flammable gas and storage requirements in 1910.106.
• Also avoid open flames, ensure proper signage, and store BD away from incompatible oxidizers and sources of heat.

1,3-Butadiene is incompatible with strong oxidizing agents and can form explosive compounds with copper and copper alloys (for crude BD); it can also form peroxides and polymerize if inhibitor is not maintained.

• The Appendix B reactivity section lists oxidizers and copper contact as specific incompatibilities and warns of peroxide formation and polymerization risks.
• Keep BD away from oxidizers, avoid copper-containing equipment for crude BD, and maintain inhibitors and storage practices to prevent peroxide and polymer formation.

Employers should maintain proper stabilizer (inhibitor) concentration in stored BD, check storage for self-polymerization and peroxide formation, and control heat exposure to prevent polymerization.

• The Appendix B guidance explains that inhibitors are added to BD to stop polymer formation, and loss of inhibitor or exposure to air/iron can promote dangerous peroxides or polymer plugs in piping.
• Implement monitoring of inhibitor levels, inspect containers and piping regularly, and follow supplier recommendations for inhibitor management.

OSHA classifies 1,3-Butadiene as a Class B fire hazard for compliance with fire protection requirements.

• The Appendix B guidelines explicitly state BD is classified as a Class B fire hazard for 1910.155 compliance.
• Use this classification when designing fire prevention measures, selecting extinguishing systems, and coordinating with local fire authorities.

Locations with BD present and posing an explosive atmosphere must be treated as Class I hazardous locations under the electrical classification rules.

• The Appendix B guidance states that areas classified as hazardous due to BD shall be Class I for purposes of 1910.307.
• Apply the appropriate Division and Group designations based on vapor frequency and concentration when specifying electrical equipment and wiring practices.

Use non-sparking tools and ensure metal BD containers are effectively grounded when opening or closing to prevent ignition from static or impact sparks.

• The Appendix B additional precautions require non-sparking tools for container operations and proper grounding of containers.
• Combine these procedures with good ventilation, elimination of open flames, and trained personnel to reduce ignition risk.

Employers should use engineering controls (ventilation), work practice controls, exposure monitoring, and appropriate PPE to prevent employee inhalation and contact with BD.

• The Appendix B guidance stresses ventilation and monitoring as primary controls and suggests PPE for situations with potential liquid contact.
• Implement a written exposure control plan that includes monitoring per 1910.1051(d), training, and medical surveillance if required by the standard.

Employers must advise employees of all areas and operations where exposure to BD might occur and provide training and hazard information for those areas.

• The Appendix B guidance explicitly states employers must inform employees about areas and operations with potential BD exposure.
• Ensure postings, labels, training sessions, and access to exposure monitoring results are part of the communication program.

If a BD cylinder leak cannot be safely stopped in place, remove the leaking cylinder to a safe place and repair it there or allow the cylinder to empty.

• This response is specified in the Appendix B spill and leak procedures.
• Only trained personnel should handle leaking cylinders; keep ignition sources away and follow emergency response procedures.

Piping carrying BD may become plugged by formation of rubbery polymer; to prevent this, maintain inhibitor levels, inspect piping, and control process temperatures and materials that promote polymerization.

• The Appendix B reactivity and special precautions warn of polymer formation that can plug piping and recommend monitoring inhibitor content and preventing conditions that cause polymerization.
• Develop inspection and maintenance programs, and coordinate with suppliers about inhibitor management to reduce plugging risk.

STEL monitoring must use 15‑minute samples that represent the tasks and operations most likely to exceed the STEL on each job and shift, so measurements reflect peak short‑term exposures.

• The Appendix B guidance and 1910.1051(d)(3)(iii) require these representative 15‑minute samples for STEL evaluation.
• Identify operations with potential short-term peaks, sample the breathing zone during those tasks, and repeat monitoring across shifts and jobs where the STEL is a concern.