Compressed air equipment requirements

This rule covers compressed air receivers and other compressed-air equipment used for operations such as cleaning, drilling, hoisting, and chipping, and it excludes certain situations. See 1926.306(a)(1).

• Covered: air receivers and equipment used to provide or utilize compressed air for cleaning, drilling, hoisting, chipping, and similar operations.
• Excluded: the special problems created by using compressed air to convey materials and the special problems when people work in compressed-air environments (e.g., tunnels and caissons).
• Also excluded: compressed-air machinery and equipment used on transportation vehicles such as steam railroad cars, electric railway cars, and automotive equipment (these are not the focus of this section).

Reference: Application in 1926.306(a)(1).

All new air receivers installed after the rule’s effective date must be constructed according to the 1968 edition of the A.S.M.E. Boiler and Pressure Vessel Code, Section VIII. See 1926.306(a)(2)(i).

• Practical tip: obtain manufacturer documentation showing ASME Section VIII (1968) compliance before placing a new receiver into service.

Reference: New equipment construction requirement in 1926.306(a)(2)(i).

All safety valves must be constructed, installed, and maintained in accordance with the A.S.M.E. Boiler and Pressure Vessel Code, Section VIII (1968). See 1926.306(a)(2)(ii).

• Practical actions: use safety valves rated and certified per ASME Section VIII (1968), install them per the manufacturer/ASME instructions, and include them in your maintenance schedule.

Reference: Safety valve construction and maintenance requirement in 1926.306(a)(2)(ii).

Air receivers must be installed so that drains, handholes, and manholes are easily accessible; they must not be buried underground or placed in inaccessible locations. See 1926.306(b)(1).

• Practical guidance: locate receivers in mechanical rooms or outdoor pads with clear access, lighting, and safe walking surfaces so crews can inspect and service drains and openings.

Reference: Installation requirements in 1926.306(b)(1).

Every air receiver must have a drain pipe and valve at its lowest point to remove accumulated oil and water; adequate automatic traps may be used in addition to the drain valve, and the receiver must be drained frequently to prevent excessive liquid buildup. See 1926.306(b)(2).

• Practical actions:
  • Install a drain valve at the lowest point and consider automatic traps to reduce manual intervention.
  • Establish and document a draining schedule (e.g., daily or more often depending on duty cycle and condensate levels).
  • Cycle drains during shutdowns or install automatic timed drains when frequent manual draining is impractical.

Reference: Drains and traps requirement in 1926.306(b)(2).

Every air receiver must have an indicating pressure gauge (located to be readily visible) and one or more spring-loaded safety valves whose total relieving capacity prevents the receiver pressure from exceeding its maximum allowable working pressure (MAWP) by more than 10 percent. See 1926.306(b)(3)(i).

• Practical steps:
  • Mount a clearly visible pressure gauge near the operator or service area.
  • Size safety valves so total relieving capacity keeps pressure ≤ MAWP × 1.10 under overpressure conditions; consult the pressure vessel manufacturer or an ASME-qualified engineer for sizing.

Reference: Gages and safety valves in 1926.306(b)(3)(i).

No—no valve of any type may be placed between the air receiver and its safety valve(s). See 1926.306(b)(3)(ii).

• Practical implication: safety valves must have an unobstructed path to vent; do not install shutoffs, isolation valves, or other fittings upstream of the safety device that could disable it.

Reference: Prohibition on valves between receiver and safety valve in 1926.306(b)(3)(ii).

Safety appliances (such as safety valves, indicating devices, and controllers) must be constructed, located, and installed so they cannot be readily rendered inoperative by any means, including exposure to the elements. See 1926.306(b)(3)(iii).

• Practical measures:
  • Protect devices with weatherproof housings or covers where appropriate.
  • Locate gauges and valves where they won’t be struck by equipment or damaged by debris.
  • Lock or secure adjustment mechanisms to prevent accidental or unauthorized tampering.

Reference: Protection of safety appliances in 1926.306(b)(3)(iii).

Safety valves must be tested frequently and at regular intervals to ensure they are in good operating condition. See 1926.306(b)(3)(iv).

• Practical steps:
  • Adopt a written testing schedule (for example, monthly, quarterly, or annually depending on service conditions and manufacturer recommendations).
  • Record each test, inspector, date, and result; repair or replace valves that fail.
  • Follow manufacturer and ASME guidance for test procedures and relieving-valve maintenance.

Reference: Testing requirement in 1926.306(b)(3)(iv).

The standard covers compressed air used for cleaning operations, but it does not address all hazards of using compressed air on people or clothing; employers must assess hazards and control them appropriately. See 1926.306(a)(1).

• Important compliance point: when compressed air is used for cleaning people or clothing there are additional hazards (eye or skin injury, air embolism, aerosolizing contaminants). Employers must evaluate the task and provide controls and PPE as required. OSHA’s PPE hazard assessment guidance explains that employers must assess hazards and, where PPE is required, provide and certify appropriate PPE selection; see OSHA’s interpretation on PPE hazard assessment (2024-03-28 Letter of Interpretation).

References: Application of 1926.306(a)(1) and PPE hazard assessment interpretation (2024-03-28).

No—1926.306(a)(1) states that this section does not deal with the special problems created by using compressed air to convey materials, so those situations are not covered by this particular section. See 1926.306(a)(1).

• Practical note: if your operation uses compressed air to convey materials, consult other industry standards and engineering guidance to address the unique hazards of pneumatic conveying.

Reference: Exclusion in 1926.306(a)(1).

No—1926.306(a)(1) specifically states the section is not intended to apply to compressed-air machinery and equipment used on transportation vehicles such as steam railroad cars, electric railway cars, and automotive equipment. See 1926.306(a)(1).

• Practical implication: mobile or vehicle-mounted compressed-air equipment may be covered by other standards or manufacturer guidance; verify obligations that apply to vehicle equipment.

Reference: Exclusion for transportation vehicles in 1926.306(a)(1).

Automatic traps may be installed in addition to drain valves, but the regulation requires a drain pipe and valve at the lowest point of every air receiver; automatic traps can supplement but do not eliminate the need for proper draining. See 1926.306(b)(2).

• Best practice: keep a manual drain valve accessible for maintenance and inspection even if automatic drains are installed, and document drain operation and frequency.

Reference: Drains and traps in 1926.306(b)(2).

It means the combined relieving capacity of the installed safety valves must be sufficient so that, under overpressure conditions, the pressure in the receiver does not rise above the maximum allowable working pressure (MAWP) plus 10 percent. See 1926.306(b)(3)(i).

• Practical guidance:
  • Determine the receiver’s MAWP from nameplate or manufacturer documentation.
  • Have safety valves sized and set so the valves will vent enough flow to keep pressure ≤ MAWP × 1.10 during an overpressure event; consult ASME/valve manufacturer for sizing and selection.

Reference: Relieving capacity requirement in 1926.306(b)(3)(i).

The standard requires that safety valves be tested frequently and at regular intervals but does not prescribe a specific recordkeeping format; employers should maintain written testing and maintenance records as part of their safety program to show compliance. See 1926.306(b)(3)(iv).

• Practical steps:
  • Keep dated records of valve tests, repairs, and replacements, and of receiver drain actions.
  • Use records to set appropriate testing intervals and to demonstrate a maintenance history during inspections.

Reference: Testing frequency requirement in 1926.306(b)(3)(iv).

The employer is responsible for ensuring safety appliances, indicating devices, and controls are constructed, located, and installed so they cannot be readily rendered inoperative (including by weather or other elements). See 1926.306(b)(3)(iii).

• Typical protections include:
  • Weatherproof housings for outdoor gauges/controls.
  • Guarding to prevent impact damage from tools or equipment.
  • Secured mounting and tamper-resistant fasteners to prevent accidental or unauthorized adjustment.
  • Regular inspection as part of preventive maintenance to detect degradation.

Reference: Protection requirement in 1926.306(b)(3)(iii).