Ventilation requirements in construction

Under 1926.57(a), you must use ventilation whenever hazardous dusts, fumes, mists, vapors, or gases exist or are produced during construction work and their concentrations could exceed the exposure limits in 1926.55(a). Employers must install and operate ventilation systems as an engineering control when ventilation is used to meet those limits. See Requirement in 1926.57(a) and the exposure limits in 1926.55(a).

• If measured or likely concentrations may exceed the limits in 1926.55(a), control by ventilation is required unless another effective control is used.
• Ventilation is treated as an engineering control and must be designed and maintained accordingly.

Under 1926.57(a), ventilation can be used as the engineering control method but only if it keeps airborne contaminant concentrations at or below the limits in 1926.55(a). If ventilation alone cannot maintain exposures below those limits, additional controls (local exhaust, substitution, enclosure) or respiratory protection under a program are required. See 1926.57(a) and 1926.55(a).

• Verify effectiveness with air monitoring or exposure assessment.
• If ventilation cannot adequately control exposure, implement other controls or a respiratory protection program per 1926.103.

Under 1926.57(b) and 1926.57(c), local exhaust ventilation must be designed to prevent dispersion of dusts, fumes, mists, vapors, and gases into the work air and must maintain sufficient exhaust volume and velocity to capture contaminants and convey them to safe disposal points. See 1926.57(b) and 1926.57(c).

• Hoods, ducts, fans and separators must be sized and placed so contaminants are captured at the source (not dispersed).
• Ducting and collectors must convey contaminants to safe outdoor discharge or approved disposal (see 1926.57(e)).
• Systems must be maintained and operated to preserve capture velocity and airflow (see 1926.57(c)).

Under 1926.57(c), exhaust systems must be designed so contaminated air is not drawn through employees' work areas. The system should capture contaminants at the source and move them away without creating a contaminated path through the workspace. See 1926.57(c).

• Arrange hoods and airflow so intake does not pull contaminants past other workers.
• Use local exhaust or containment so the contaminated airstream travels directly to dust collectors or outside discharge points.

Under 1926.57(d)(1)–(2), the exhaust system must run continuously during the operations it serves and, if employees remain in the contaminated zone, it must continue after operations cease for a time sufficient to remove suspended respirable dusts and other contaminants. See 1926.57(d)(1) and 1926.57(d)(2).

• Microscopic dust can remain suspended for hours in still air, so continued ventilation is essential.
• Determine post-operation run-time based on contaminant type, particle size, enclosure volume, and system effectiveness; document the basis in your procedures.

Under 1926.57(e), recirculating air back into the work area is only acceptable if the concentrations that accumulate do not result in harmful exposure to employees; otherwise all collected air must discharge outdoors. See 1926.57(e).

• If you plan to recirculate, verify contaminant concentrations after filtration and show they remain below relevant limits in 1926.55(a).
• Use appropriate dust collectors/filters (HEPA or equivalent) and monitor regularly to ensure safe concentrations before returning air.

Under 1926.57(f), dust and refuse from exhaust systems must be disposed of so they do not cause harmful exposure to employees; collectors must be set up and emptied without contaminating other work areas. See 1926.57(f) and 1926.57(f)(5).

• Use sealed containers or enclosed collection points for dust removal.
• Clean and empty dust collectors in controlled locations with local exhaust or respirators as needed.
• Follow procedures that prevent re-suspension during transfer or disposal.

Under 1926.57(f)(5)(i), employers must use only respirators approved by NIOSH under 42 CFR part 84 to protect employees from dusts produced during abrasive-blasting operations. See 1926.57(f)(5)(i).

• Ensure the respirator is NIOSH-approved for the specific contaminant and use (supplied-air abrasive-blasting respirators are commonly required).
• Maintain, inspect, and fit-test respirators per the employer's respiratory protection program in 1926.103.

Under 1926.57(f)(5)(ii), abrasive-blasting operators must wear abrasive-blasting respirators when working inside blast-cleaning rooms, when using silica sand in manual blasting where the operator is not physically separated in an exhaust-ventilated enclosure, or where toxic dust concentrations may exceed limits in 1926.55 and the operator is not physically separated. See 1926.57(f)(5)(ii)(A–C).

• If the operator is inside the enclosure or exposed to silica sand or potential over-limit toxic dusts, a full abrasive-blasting respirator that covers head/neck/shoulders is required.
• Choose respirators that match the hazard and follow the respiratory program in 1926.103.

Under 1926.57(f)(5)(iii), properly fitted particulate-filter respirators may be used only for short, intermittent, or occasional dust exposures—such as cleanup, emptying dust collectors, or unloading shipments—when it's not feasible to control dust by enclosure or ventilation. See 1926.57(f)(5)(iii).

• For prolonged or continuous exposures, supplied-air or abrasive-blasting respirators are required.
• Even for short tasks, the respirator must be NIOSH-approved and used under a written respiratory protection program per 1926.103.

Under 1926.57(f)(5)(iv) and 1926.103, employers must establish a respiratory protection program whenever respiratory protective equipment is necessary to protect employees during abrasive-blasting operations. The program must meet the requirements in 1926.103. See 1926.57(f)(5)(iv).

• The program must include medical evaluation, fit testing, training, respirator selection, maintenance, and supervision as detailed in 1926.103.
• Keep records and ensure only NIOSH-approved respirators are used per 1926.57(f)(5)(i).

Under 1926.57(f)(6), air supplied to abrasive-blasting respirators must be free of harmful quantities of dusts, mists, or noxious gases and must meet the supplied-air quality requirements in 29 CFR 1910.134(i). See 1926.57(f)(6).

• Compressed air and breathing air systems must be filtered and tested per 1910.134(i).
• Maintain and test compressors, filters, and lines regularly to ensure breathable air quality.

Under 1926.57(f)(3)(i) and subparts (A)–(E), blast-cleaning enclosures must have exhaust ventilation that maintains continuous inward airflow at all openings during blasting; inlets and openings must be baffled to minimize escape; exhaust rates must clear dust promptly after blasting; blast must be turned off and exhaust run long enough to clear dust before opening; and baffles and doors must be secure and inspected. See 1926.57(f)(3)(i) and 1926.57(f)(3)(i)(A–E).

• Always run exhaust after blasting until air inside enclosure is clear before allowing entry or opening doors.
• Install slit abrasive-resistant baffles on small openings and inspect/replace them regularly (1926.57(f)(3)(i)(E)).

Under 1926.57(f)(4)(i), the construction, installation, inspection, and maintenance of exhaust systems for blasting must conform to the principles in ANSI Z9.2-1960 and ANSI Z33.1-1961. See 1926.57(f)(4)(i).

• Follow those ANSI principles for hood design, ducting, collection, and safe discharge.
• Make repairs promptly when dust leaks are noted (1926.57(f)(4)(i)(a)).
• Check static pressure drop after installation and periodically to ensure continued performance (1926.57(f)(4)(i)(b)).

Under 1926.57(f)(4)(ii)–(iii), if the abrasive is recirculated, the exhaust ventilation must not be relied upon to remove fines—instead, provide a dedicated abrasive separator; and exhaust air from blast equipment must be discharged through dust collecting equipment. See 1926.57(f)(4)(ii) and 1926.57(f)(4)(iii).

• Use an abrasive separator to remove fines from spent abrasive before recirculation.
• Ensure dust collectors handle the exhausted air to prevent worker exposure.

Under 1926.57(f)(4)(i)(b) and related paragraphs, an appreciable change in static pressure drop (indicating partial blockage) should trigger cleaning and maintenance to restore normal operation. Static pressure should be checked at installation and periodically thereafter. See 1926.57(f)(4)(i)(b).

• Monitor pressure drop as part of routine inspection; when it increases noticeably, clean ducts, hoods, and collectors.
• Repair dust leaks promptly per 1926.57(f)(4)(i)(a).

Under 1926.57(f)(2)(ii) and 1926.55, you must keep respirable dust or fume concentrations in the breathing zone of blasting operators and other workers below the limits in [1926.55] by using enclosure, local exhaust, dust collectors, separators, and respirators when needed. See 1926.57(f)(2)(ii) and 1926.55.

• Monitor worker exposures and adjust controls if limits are approached or exceeded.
• If engineering controls cannot maintain compliance, implement a respiratory protection program per 1926.103.

Under 1926.57(f)(2)(iii), when flammable or explosive dust mixtures may be present, use automatic systems for combustible organic abrasives only, build equipment and exhaust systems to NFPA/ANSI requirements (ANSI Z33.1-1961/NFPA 91-1961), bond and ground the nozzle to prevent static, and provide explosion venting/relief panels away from occupied areas. See 1926.57(f)(2)(iii).

• Follow NFPA guidance on explosion venting and design of dust-handling equipment.
• Ground and bond equipment to avoid static ignition; keep electrical wiring suitable for dust environments.

Under 1926.57(f)(5)(v) and (v)(A–B), abrasive-blasting operators must be equipped with heavy canvas or leather gloves and aprons (or equivalent), safety shoes meeting the listed standard, and eye/face protection when respirator design doesn't protect those areas. See 1926.57(f)(5)(v), 1926.57(f)(5)(v)(A) and 1926.57(f)(5)(v)(B).

• Provide heavy gloves and aprons to protect from abrasive impact.
• Provide safety shoes that meet ANSI Z41.1-1967 (as referenced) or current applicable footwear standards.
• Supply eye/face protection where the respirator does not cover these areas.

Under 1926.57(f)(3)(i)(D) and (E), observation windows must use safety glass protected by screening when hard, deep-cutting abrasives are used, and small access openings must have multiple sets of slit abrasive‑resistant baffles that are inspected and replaced as needed. See 1926.57(f)(3)(i)(D–E).

• Keep baffles in good condition to prevent dust escape; inspect regularly.
• Use screened safety glass to prevent flying abrasive from breaking windows and injuring observers.

Under 1926.57(e) and 1926.57(f)(4)(iii), exhaust air from blast‑cleaning equipment must be discharged to the outside atmosphere through dust collecting equipment; returning air to the work area is only allowed if recirculated concentrations are shown safe. See 1926.57(e) and 1926.57(f)(4)(iii).

• Use dust collectors or filtration before discharge; avoid emitting dust into occupied areas.
• If recirculating, verify post-filter contaminant levels are below 1926.55(a) limits.

Under 1926.57 and OSHA’s November 14, 2024 letter, asbestos work performed as part of property remediation involving asbestos‑containing building materials is covered by the construction asbestos standard, 29 CFR 1926.1101, not the general industry standard. The letter explains that remediation activities involving ACBM are subject to the construction standard. See the asbestos LOI: Asbestos remediation protocols (Nov 14, 2024) and 1926.57.

• For asbestos work, follow the engineering controls, work practices, and ventilation requirements in [1926.1101].
• Use appropriate containment, HEPA filtration, and regulated disposal to prevent exposure during cleanup and ventilation.

Under [29 CFR 1910.134] and OSHA’s July 16, 2024 letter, the respiratory standard’s oxygen‑deficient threshold (below 19.5% O2) applies to civilian employees covered by OSHA, and an oxygen‑deficient atmosphere must be treated as IDLH; however, military-unique systems and personnel may be excluded. See 1910.134 and the LOI: Oxygen-deficient atmospheres in HVAC (July 16, 2024).

• For civilian construction and contractor work, design HVAC and ventilation to prevent oxygen‑deficient conditions and follow [1910.134] requirements if workers may enter such atmospheres.
• For military-unique facilities, consult the LOI text because certain military operations are outside OSHA jurisdiction.

Under [1926.57] and the respiratory protection program requirements in [1926.103], you must first try to control exposures with engineering (ventilation, enclosure, local exhaust) to keep contaminant levels below [1926.55(a)] limits; if ventilation cannot do this or during temporary conditions where controls are infeasible, you must provide appropriate respirators under a written program in [1926.103]. See 1926.57(a) and 1926.103.

• Perform exposure monitoring to decide if ventilation alone is adequate.
• If respiratory protection is necessary, implement medical evaluations, fit testing, training, and maintenance per [1926.103].

Under [1926.57(f)(5)(ii)(B)], when silica sand is used in manual blasting operations where the nozzle and blast are not physically separated from the operator by an exhaust‑ventilated enclosure, the operator must wear an abrasive‑blasting respirator. See 1926.57(f)(5)(ii)(B).

• Because silica dust causes serious lung disease, use supplied‑air abrasive‑blasting respirators and a full respiratory program per [1926.103].
• Consider substituting silica sand with a less hazardous abrasive or using automated/enclosed systems to eliminate the need for manual blasting.

Under [1926.57(f)(3)(i)(E)(1)–(2)], doors on blast‑cleaning rooms must be flanged and tight when closed, and doors must be operable from both inside and outside except that small operator access doors may allow the large work access door to be opened from the outside only. See 1926.57(f)(3)(i)(E)(1–2).

• Ensure doors seal well to maintain inward airflow and prevent dust escape.
• Provide means of egress and door operation consistent with safety (inside-outside operability as required).

Under [1926.57(f)(1)(ix)–(xii)], important definitions include "Dust collector," "Particulate‑filter respirator," "Rotary blast cleaning table," and "Abrasive blasting," which affect ventilation and PPE choices. See the definitions in 1926.57(f)(1)(ix–xii).

• Knowing these definitions helps determine when dust collectors, supplied‑air respirators, enclosures, or separators are required.
• For example, "abrasive blasting" specifically covers forcible application by pneumatic, hydraulic, or centrifugal force, which triggers the blasting paragraph requirements.

Local exhaust ventilation must be provided whenever dry grinding, polishing, or buffing is performed and employee exposure (even if they wear respirators) exceeds the permissible exposure limits. See 1926.57(g)(2).

• This means you must measure exposures against the PELs in 1926.55 and install a local exhaust system if exposures exceed those limits.
• Local exhaust is required regardless of respirator use; respirators do not substitute for ventilation under this paragraph.

Hoods must be designed, located, and placed so dust and dirt are carried into the hood by the airflow and not thrown into the operator's breathing zone. See 1926.57(g)(3)(i).

• Position the hood so the particle travel is toward the hood inlet, not toward the operator.
• Do not run wheels, discs, belts, or straps in a direction that throws dust into the operator’s breathing zone.

The recommended minimum duct velocity is 4,500 feet per minute (fpm) in the branch (hood) and 3,500 fpm in the main (header) duct. See 1926.57(g)(3)(ii).

• Use these velocities when sizing ducts so dust stays suspended to the exhaust fan and separations work effectively.
• Table D-57.1 gives the minimum exhaust volumes for many wheel types; use both volume and velocity requirements when designing systems.

For a grinding wheel over 9 to 16 inches in diameter with a 2-inch width, the minimum exhaust volume is 390 cubic feet per minute (cfm). See 1926.57(g)(3)(ii) and Table D-57.1 in 1926.57.

• Confirm your hood and branch duct are sized to achieve that cfm and the recommended branch duct velocity of 4,500 fpm.

Use Table D-57.2 to find the minimum exhaust volume for buffing and polishing wheels based on disc diameter and wheel width; the standard requires at least the volume shown. See 1926.57(g)(3)(iii).

• Match your wheel’s diameter and width to Table D-57.2 in 1926.57.
• If the wheel width differs from the table entry, use the rule in 1926.57(g)(3)(iii) for adjustments (see next question for the calculation method used for grinding wheels, which the standard uses similarly).

Increase the exhaust volume in proportion to the ratio of the actual wheel width to the width shown in the table. See 1926.57(g)(3)(iii).

• Example: For a wheel 4.5 inches wide where the table uses 4 inches and the table volume is 610 cfm, calculate 4.5 ÷ 4 × 610 = 686 cfm (rounded to 690 cfm in the standard’s example).
• Apply the same proportional increase logic to buffing/polishing wheels when needed and documented by the standard.

Horizontal single-spindle disc grinders must be hooded and connected to branch pipes that provide the exhaust volumes listed in Table D-57.3. See 1926.57(g)(3)(iv).

• For example, a disc up to 12 inches requires 220 cfm, over 12 to 19 inches requires 390 cfm, and so on as shown in Table D-57.3 in 1926.57.
• Make sure the hood fully captures dust and the branch duct meets the specified cfm and velocity recommendations.

Horizontal double-spindle disc grinders must have a hood enclosing the grinding chamber and be connected to branch pipes providing the exhaust volumes shown in Table D-57.4. See 1926.57(g)(3)(v).

• Use the table entries for the disc diameter to select the required cfm (e.g., up to 19 inches = 610 cfm, over 19 to 25 inches = 880 cfm).
• Ensure the hood and ducting provide the required capture and conveyance velocities.

The required exhaust volume depends on the disc diameter and whether one-half or more of the disc is covered by the hood; the number of outlets or equal distribution can meet the table's requirements. See 1926.57(g)(3)(vi) and Table D-57.5 in 1926.57.

• Table D-57.5 lists exhaust cfm for different diameters and for configurations where one-half or more of the disc is covered vs. where the disc is not covered.
• The table also notes the "Number" of exhaust outlets around the periphery or equal distribution by other means—design your system to meet that distribution and total cfm.

No. The standard explicitly does not apply to steam blasting, steam cleaning, or hydraulic cleaning methods where work is done without the aid of abrasives. See 1926.57.

• If the operation uses abrasives or creates airborne dust from grinding/polishing, then the grinding ventilation rules do apply.

The standard defines abrasive cutting-off wheels as organic-bonded wheels with thickness limits relative to diameter and used for cutting-type operations, and it defines belts as power-driven, flexible, coated bands used for grinding, polishing, or buffing. See 1926.57(g)(1)(i) and 1926.57(g)(1)(ii).

• These definitions affect which equipment types are covered by the ventilation requirements in paragraph (g).

Operating wheels, discs, straps, or belts in a direction that causes dust and dirt to be thrown into the operator's breathing zone is specifically prohibited. See 1926.57(g)(3)(i).

• Ensure machine setup and rotation direction move dust into the hood, not toward the operator.
• If redesigning the operation doesn't prevent particle projection into the breathing zone, provide appropriate local exhaust per the standard.

Entry losses (static pressure losses at hood inlets) must equal 0.65 velocity pressure for a straight takeoff and 0.45 velocity pressure for a tapered takeoff for all hoods except the vertical-spindle disc grinder hood. See the entry loss requirements in 1926.57(g)(3)(ii) and the following paragraph in 1926.57.

• The vertical-spindle disc grinder hood entry loss is shown in Figure D-57.1 (referenced in the standard text).
• Use these entry loss factors when calculating fan sizing and duct design to ensure required capture velocities are achieved.

An exhaust system consists of branch pipes connected to hoods or enclosures, one or more header (main) pipes, an exhaust fan, particulate separation means, and a discharge stack to the outside; a branch pipe is the pipe connected directly to the hood, while a header pipe is the main pipe into which branch pipes enter. See 1926.57(g)(1)(vii) and 1926.57(g)(1)(ix).

• Proper system design must consider branch cfm (from tables) and main/header conveyance velocity (recommended 3,500 fpm).
• Include separators (filters, cyclones) and an outdoor discharge per the standard.

Hoods and enclosures are the partial or complete enclosures around the wheel or disc through which air enters an exhaust system during operation. See 1926.57(g)(1)(x).

• Design them to capture dust at source and direct flow into the branch pipe at the required velocity.

Grinding wheels are defined as power-driven rotatable abrasive wheels (not disc wheels) made of abrasive particles held by bonds and used for peripheral grinding; these are subject to the paragraph (g) ventilation requirements. See 1926.57(g)(1)(viii).

• Disc wheels and other defined wheel types have their own specific hooding and exhaust-volume requirements elsewhere in paragraph (g).

Employers must provide exhaust volumes not less than the minimums shown in Table D-57.1 and a recommended minimum duct velocity of 4,500 fpm in the branch and 3,500 fpm in the main. See 1926.57(g)(3)(ii).

• Select the correct table row by wheel diameter and ensure the hood/branch duct meets the listed cfm and velocity.
• Document system performance to show compliance with the table values.

No. Employers cannot rely solely on respirators—local exhaust ventilation must be provided where exposures exceed permissible limits regardless of respirator use. See 1926.57(g)(2) and the applicable exposure limits in 1926.55.

• Respirators may be part of a protection strategy, but paragraph (g)(2) requires ventilation if PELs are exceeded even with respirators.

Yes. Portable grinders are defined and covered by the paragraph (g) requirements, but the standard provides specific minimum exhaust volumes and hooding rules primarily for floor stands, benches, disc grinders, and similar machines—portable grinders should be controlled by hoods or exhaust appropriate to the operation as required in 1926.57(g).

• For portable operations, implement local exhaust or other controls that achieve compliance with exposure limits in 1926.55 and the guidance in paragraph (g) about hood placement and airflow.

The standard lists the minimum exhaust volumes in the tables following paragraph (g): Table D-57.1 for grinding and abrasive cutting-off wheels, Table D-57.2 for buffing and polishing wheels, Table D-57.3 for horizontal single-spindle disc grinders, Table D-57.4 for horizontal double-spindle disc grinders, and Table D-57.5 for vertical spindle disc grinders. See 1926.57(g)(3)(ii) and the tables in 1926.57.

• Use the appropriate table for your equipment type and wheel/disc diameter (and width where applicable) to determine required cfm.

You must redesign hooding or change the operation so the dust is projected into the hood by the airflow and not into the operator’s breathing zone; operating wheels in a way that throws dust into the operator is prohibited. See 1926.57(g)(3)(i).

• Solutions include reorienting the wheel rotation, repositioning the hood, adding local exhaust, or changing work practices so particles move toward the hood inlet.

A 6-inch (15.24 cm) wide grinding or polishing belt requires 390 cubic feet per minute (ft3/min) of exhaust through the hood’s branch pipe, and the hood must be provided to remove dust and dirt generated and be connected to the branch pipe specified in the standard. See the requirement in 1926.57(g)(3)(vii).

• The exhaust volumes are listed in Table D‑57.6; examples from that table are:
  • Up to 3 in (7.62 cm) — 220 ft3/min
  • Over 3 to 5 in (7.62–12.7 cm) — 300 ft3/min
  • Over 5 to 7 in (12.7–17.78 cm) — 390 ft3/min (this covers a 6‑inch belt)
  • Over 7 to 9 in — 500 ft3/min, etc.
• Hoods must actually remove the dust produced and be connected to branch pipes sized to deliver the volumes in Table D‑57.6; where the work is performed outside the hood, required air volumes must be increased as described in 1926.57(g)(3)(ix).
• Also follow the hood-construction and placement guidance (hoods should be as close to the operation as practicable) in the hood-design provisions of 1926.57(g)(5), such as 1926.57(g)(5)(x).

Portable grinding operations conducted within a partial enclosure must have an average face air velocity of at least 200 feet per minute, and cradle or swing-frame grinders require a minimum average air velocity of 150 feet per minute over the entire enclosure opening; the operator must be positioned outside the working face of the enclosure. See 1926.57(g)(5)(iv) and 1926.57(g)(3)(viii).

• Portable grinding: keep the enclosure opening no larger than actually required and maintain an average face air velocity of not less than 200 ft/min into the opening (1926.57(g)(5)(iv)).
• Cradle and swing-frame grinders: when cradles require large partial enclosures, maintain a minimum average air velocity of 150 ft/min over the entire opening; swing-frame grinders must be exhausted the same way as cradles (1926.57(g)(3)(viii)).
• Operator location: the operator must be positioned outside the working face of the enclosure, and the face opening should be no larger than actually required for the operation; an average intake air velocity of not less than 150 ft/min applies where specified (1926.57(g)(5)(vii)).