Welding Fume OSHA Requirements: Hexavalent Chromium, Manganese, Ventilation, and Air Monitoring

Welding fume isn’t a single hazard. It’s a mixture of metal oxides, gases, and particulates that changes composition depending on what you’re welding, how you’re welding it, and what coatings or treatments are on the base metal. The standard advice, “provide ventilation,” doesn’t cover what OSHA actually requires for stainless steel, coated metals, or confined space welding operations.

Here’s what the regulations say and what you actually need to do.

What Welding Fumes Contain

Carbon steel welding produces fumes that are primarily iron oxide by mass. That’s not harmless, but it’s the least toxic of the common welding scenarios. The OSHA PEL for iron oxide fumes is 10 mg/m³ as an 8-hour TWA under the Z-table limits in 1910.1000.

Stainless steel welding is a different problem entirely. Stainless steel contains chromium, and when you arc-weld stainless, some of that chromium oxidizes into hexavalent chromium (Cr(VI)), a confirmed human carcinogen. The amount depends on the stainless alloy, the welding process, and the shielding gas. GTAW (TIG) welding generally produces lower Cr(VI) than GMAW (MIG) or SMAW (stick), but no stainless welding process is Cr(VI)-free.

Mild steel welding contains manganese from the filler metals and base metal. Most carbon steel electrodes contain 1 to 2 percent manganese. Manganese fume is the neurotoxin in welding fume. Chronic exposure is associated with manganism, a Parkinson’s-like neurological condition. Unlike lead or chromium, manganese doesn’t have a clear biological marker to detect early damage, which makes the OSHA PEL inadequate as a health standard.

Galvanized steel adds zinc oxide to the picture. The galvanizing coating burns off during welding and produces zinc oxide fumes that cause metal fume fever, an acute flu-like syndrome with chills, fever, and muscle aches that typically resolves within 24 to 48 hours. It’s rarely fatal but it’s common and it’s preventable.

Coated or painted metals are the most unpredictable. Lead-based paint, cadmium plating, and various primers all release their own hazardous fumes when subjected to arc heat. Before welding any coated material, you need to know what the coating is.

Hexavalent Chromium: OSHA’s Most Specific Welding Fume Standard

OSHA 1910.1026 (general industry) and 1926.1126 (construction) set specific requirements for hexavalent chromium exposures, including welding operations that generate Cr(VI).

The PEL is 5 micrograms per cubic meter (5 µg/m³) as an 8-hour TWA. The action level is 2.5 µg/m³.

Crossing the action level triggers a cascade of obligations. You need air monitoring, employee notification of exposure results, medical surveillance, and written exposure records. Crossing the PEL adds a respiratory protection requirement on top of the engineering controls you’re already supposed to have in place.

In poorly ventilated conditions, stainless steel welding can produce Cr(VI) exposures of 30 to 100 µg/m³ or higher. Even with basic ventilation, exposures above the action level are common. Initial air monitoring on stainless steel welding operations should be considered standard practice, not optional.

The 1910.1026 standard also requires a written Cr(VI) compliance program when exposures exceed the PEL, including a description of engineering controls, work practices, and the respiratory protection selection rationale.

Manganese: The PEL Gap Problem

OSHA’s general industry PEL for manganese is 5 mg/m³ as a ceiling limit, set in the 1971 Z-tables and never updated through a formal rulemaking. That limit was based on preventing acute toxicity, not chronic neurological disease.

The NIOSH recommended exposure limit (REL) for manganese is 0.1 mg/m³ as a 10-hour TWA. The ACGIH Threshold Limit Value (TLV) for manganese is 0.02 mg/m³ inhalable fraction. Those limits reflect the actual health data on manganism risk, but they’re not legally enforceable by OSHA.

The practical implication: a welding operation can comply with OSHA’s manganese PEL while still exposing workers to levels that NIOSH and ACGIH consider hazardous. This is exactly the kind of situation where OSHA’s general duty clause (Section 5(a)(1)) can be applied. If you’re aware of NIOSH and ACGIH guidance on manganese and don’t act on it, that’s an elevated enforcement risk.

The right approach is to measure actual manganese exposures with personal air monitoring, compare results against NIOSH and ACGIH limits, and implement local exhaust ventilation when exposures exceed those more protective limits, even if OSHA’s PEL is technically met.

Zinc Oxide and Metal Fume Fever

Welding galvanized steel is where metal fume fever happens. It’s common, it’s preventable, and most workers who get it don’t know what caused it.

Zinc oxide fumes are released when the galvanized coating burns off. The onset of metal fume fever typically happens 4 to 12 hours after exposure. Workers go home feeling fine and wake up at midnight with chills, fever, muscle aches, and nausea. Most recover within 24 to 48 hours. Repeated exposure builds temporary tolerance, which can lead workers to underestimate the hazard.

OSHA 1910.252(c)(5) specifically requires special precautions for welding on metals with coatings that produce toxic fumes, including zinc. The requirement is to use local exhaust ventilation or to move the work outdoors with positioning so the wind carries fumes away from the welder’s breathing zone. “Outdoors with wind at your back” is a control, but not a reliable one. LEV is better.

The OSHA PEL for zinc oxide fumes is 5 mg/m³ as a ceiling limit under the Z-tables. That’s the line you can’t cross legally. But metal fume fever can occur at lower concentrations, particularly in workers who haven’t developed tolerance.

Ventilation Requirements

OSHA 1910.252 is the base standard for welding, cutting, and brazing. It requires mechanical ventilation in three specific situations:

• Welding in a confined space (always).
• Welding metals with hazardous coatings (zinc, lead, cadmium, chromium, etc.).
• Any space where the work area is less than 10,000 cubic feet per welder, or where the ceiling is lower than 16 feet, or where the workspace is partitioned and there isn’t cross ventilation.

For operations that don’t meet those triggers, natural ventilation may be adequate for mild steel welding in open shops. But “may be adequate” isn’t a compliance strategy. You need to know the actual exposure levels to make that determination.

Local exhaust ventilation (LEV) is the preferred control for stainless steel and coated metal welding. LEV captures fumes at the source before they enter the breathing zone. The two main approaches are:

Fume extraction guns integrate the exhaust capture directly into the welding gun. They capture fumes within a few inches of the arc. They’re effective for GMAW operations and add minimal complexity. The tradeoff is they require a vacuum system and slightly change the ergonomics of the gun.

Backdraft hoods or flanged exhaust hoods positioned close to the weld (within 12 to 18 inches) capture rising fume plumes effectively when work can be positioned in front of them. They’re less effective for positional welding where the welder’s body is between the fume source and the hood.

General dilution ventilation, such as shop exhaust fans and air makeup, reduces ambient fume concentration but doesn’t prevent fumes from passing through the welder’s breathing zone first. It’s a supplement to LEV, not a replacement for it.

Air Monitoring: When and How

For stainless steel or coated metal welding operations, initial personal air monitoring is the only way to know whether engineering controls are working. Guessing that ventilation is adequate isn’t a defensible position in an OSHA inspection or in litigation after a worker is diagnosed with lung cancer.

Personal air monitoring for Cr(VI) uses a sampling pump drawing air through a PVC or mixed cellulose ester filter at 1 to 3 liters per minute. The sample runs for a full shift. The filter is sent to an accredited laboratory for analysis using NIOSH Method 7703 or EPA Method 0061. Results come back in micrograms per cubic meter.

Manganese monitoring uses similar sampling pumps and filter media, analyzed by ICP-MS or ICP-OES at the lab. NIOSH Method 7300 is the standard analytical method.

If initial monitoring shows exposures below 50 percent of the applicable action level and exposure conditions won’t change, you can establish periodic monitoring on a longer interval. If exposures are above the action level, monitoring must continue at least every 6 months for Cr(VI).

You don’t need a CIH to conduct sampling, but the interpretation of results and the decision about what controls to implement benefits from one. If exposures are borderline, the context of measurement conditions, work duration, and control effectiveness matters significantly for the compliance decision.

Respiratory Protection for Welding Fumes

When engineering controls can’t get exposures below the PEL, or while controls are being installed, respiratory protection is required. Under OSHA’s respiratory protection standard at 1910.134, this means a written respiratory protection program, medical clearance, fit testing, and training.

For general welding fumes (iron oxide, mild steel), a half-face air-purifying respirator with P100 particulate filters provides adequate protection at typical exposure levels. The assigned protection factor (APF) for a half-face APR is 10, meaning it reduces exposure by 90 percent. For a welder exposed to 5 mg/m³ of iron oxide fumes, a half-face P100 brings exposure below the PEL.

For Cr(VI) exposures above the PEL, a half-face APR with a P100 filter may not be sufficient depending on the actual exposure concentration. If the measured exposure is 50 µg/m³ and the PEL is 5 µg/m³, you need an APF of at least 10, which a half-face APR provides. But if exposure is 500 µg/m³, you need a PAPR or supplied-air respirator with a higher APF.

Supplied-air respirators (SARs) with a loose-fitting hood or helmet are practical for welding because they don’t require fit testing and work well with welding helmets. They’re the right choice for heavy stainless steel welding in enclosed spaces or whenever air monitoring shows Cr(VI) exposures well above the PEL.

Medical Surveillance Under 1910.1026

The Cr(VI) standard triggers mandatory medical surveillance for workers exposed at or above the action level for 30 or more days per year. It also applies when a worker shows signs or symptoms of Cr(VI)-related health effects regardless of exposure level.

The medical examination includes a medical and work history with emphasis on Cr(VI) exposures, a physical exam focused on the respiratory system and skin, a pulmonary function test, and a chest X-ray for workers with 10 or more years of Cr(VI) exposure. Examinations are required before assignment, annually during exposure, and at termination of assignment.

The employer pays for all medical examinations. The physician provides a written opinion to the employer without revealing confidential medical findings. The employee gets a copy of their exam results.

Confined Space Welding

Welding in a confined space, including tanks, vessels, pits, and similar structures, requires mechanical ventilation under 1910.252(b)(4). This isn’t discretionary. The air circulation in a confined space is insufficient to dilute welding fumes under any normal welding workload.

The ventilation requirement intersects with your permit-required confined space program under 1910.146. Hot work in a permit space requires:

• Air monitoring before entry and continuously during welding.
• Continuous mechanical ventilation.
• An attendant outside the space who maintains communication with the welder.
• Rescue procedures and equipment positioned for immediate use.
• Hot work permit signed off by an authorized supervisor.

The atmosphere inside a tank being welded can reach explosive concentrations of gases from coatings, residual contents, or welding processes that use shielding gas. The hazardous fume problem and the flammability problem run together in confined space welding. Your written permit needs to address both.