Welding Fume Regulations and Exposure Limits in Ontario

Last updated in June 2024

We have been a pioneer in North America, providing welding fume extraction solutions since the 1980s. In this blog post, you will find the exposure limits applicable in Ontario for some of the most common hazardous metals and gases found in welding fume.

Fumes are formed when a metal is heated above its boiling point, and its vapors condense into very fine particles. Their size ranges from 0.005 to 20 µm, but most are smaller than 1 µm and may deposit throughout the respiratory system.

The fume composition depends on the material being welded, the electrode, the coatings, the flux, and the shielding gas, among other things. Air sampling is usually necessary to know which hazardous and regulated substances are in your working environment. But getting information on the composition of metals, gases, and consumables used in the welding process is usually a good start.

What particulates are potentially dangerous in welding fume?

Here is a list of some dangerous metals and gases commonly found in welding fume that will be covered on this page:

• Aluminum
• Antimony
• Arsenic
• Beryllium
• Cadmium
• Chromium
• Cobalt
• Copper
• Iron oxide
• Lead
• Manganese (learn more about manganese in welding fumes)
• Molybdenum
• Nickel
• Silver
• Tin
• Titanium dioxide
• Vanadium
• Zinc
• Argon
• Carbon Dioxide
• Carbon Monoxide
• Helium
• Hydrogen Fluoride
• Nitric Oxide
• Nitrogen
• Nitrogen Dioxide
• Ozone
• Phosgene

Ontario Regulation 833, Control of Exposure to Biological or Chemical Agents – Welding Fume

In Ontario, employers are required under section 4 of Regulation 833, Control of Exposure to Biological or Chemical Agents, to limit the exposure of workers to specified hazardous biological or chemical agents.

“Every employer shall take the measures required by that section to limit the exposure of workers to a hazardous biological or chemical agent in accordance with the following rules:

1. If the agent is listed in the Ontario Table, exposure shall not exceed the TWA, STEL, or C set out in the Ontario Table.

2. If the agent is not listed in the Ontario Table but is listed in the ACGIH Table, exposure shall not exceed the TWA, STEL, or C set out in the ACGIH Table.

3. If the Table that applies under paragraph 1 or 2 sets out a TWA for an agent but sets out neither a STEL nor a C for that agent, exposure shall not exceed the following excursion limits: Three times the TWA for any period of 30 minutes. Five times the TWA at any time.”

Regulation 833 also stipulates that: “An employer shall protect workers from exposure to a hazardous biological or chemical agent without requiring them to wear and use a respirator.” Which means that welding fume extractors should be used to extract pollutants at the source.

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Ontario – Occupational Exposure Limits for Welding Fume, Metals, and Gases

Based on Regulation 833, the following limits are the applicable Occupational Exposure Limits (OEL) in Ontario for welding fume and some of its components.

Abbreviations used in the tables below:

• TWA: The Time-Weighted Average concentration for an 8-hour workday and a 40-hour workweek
• STEL: Short-Term Exposure Limit (maximum time-weighted average concentration for 15 minutes, no more than four times per day, with at least 60 minutes in between)
• C: Ceiling (concentration never to be exceeded)
• (i): Inhalable dust (smaller than 100 µm)
• (r): Respirable dust (smaller than 4 µm)

OEL	TWA	STEL	C
Welding Fumes*	10mg/m3(i) 3mg/m3(r)	None	None

OEL	TWA	STEL	C
Aluminum	1mg/m3(r)	None	None
Antimony	0.5mg/m3	None	None
Arsenic	0.01mg/m3	0.05mg/m3	None
Beryllium	0.05µg/m3(i)	None	None
Cadmium	0.01mg/m3	None	None
Chromium metal & (III)	0.5mg/m3	None	None
Chromium (VI)	0.01mg/m3	None	None
Cobalt	0.02mg/m3	None	None
Copper	0.2mg/m3	None	None
Iron Oxide	5mg/m3(r)	None	None
Lead	0.05mg/m3	None	None
Manganese	0.2mg/m3	None	None
Molybdenum	3mg/m3(r) 10mg/m3(i)	None	None
Nickel	1mg/m3(i)	None	None
Silver	0.1mg/m3	None	None
Tin metal & oxide	2mg/m3	None	None
Titanium dioxide	10mg/m3	None	None
Vanadium pentoxide	0.05mg/m3(i)	None	None
Zinc oxide	2mg/m3(r)	10mg/m3(r)	None

OEL	TWA	STEL	C
Argon*	None	None	None
Carbon Dioxide	5,000ppm	30,000ppm	None
Carbon Monoxide	25ppm	None	None
Helium*	None	None	None
Hydrogen Fluoride	0.5ppm	None	2ppm
Nitric Oxide	25ppm	None	None
Nitrogen*	None	None	None
Nitrogen Dioxide	3ppm	5ppm	None
Ozone	None	None	0.1ppm
Phosgene	0.1ppm	0.3ppm	None

As a reminder, according to Regulations, “if the Table […] sets out a TWA for an agent but sets out neither a STEL nor a C for that agent, exposure shall not exceed the following excursion limits: Three times the TWA for any period of 30 minutes. Five times the TWA at any time.”

ACGIH – Threshold Limit Values for Welding Fume, Metals, and Gases

The American Conference of Governmental Industrial Hygienists (ACGIH) is an important organization researching hazardous substances and recommending exposure limits. They influence most health and safety organizations in North America and knowing their recommended Threshold Limit Values (TLV) is very valuable.

Threshold Limit Values are copyrighted by ACGIH and cannot be reproduced on other websites. However, you will find the links to the relevant pages on their website below.

ACGIH has not published a recommendation regarding welding fumes in general. Therefore, they fall under the Particulates Not Otherwise Regulated category. The ACGIH recommendation, in this case, is a TLV-TWAEV of 3mg/m3 for respirable particles and 10mg/m3 for inhalable particles.

• Aluminum
• Antimony
• Arsenic
• Beryllium
• Cadmium
• Chromium
• Cobalt
• Copper
• Iron Oxide
• Lead
• Manganese
• Molybdenum
• Nickel
• Silver
• Tin, organic
• Tin oxide & inorganic
• Titanium
• Vanadium
• Zinc Oxide
• Argon*
• Carbon Dioxide
• Carbon Monoxide
• Helium*
• Hydrogen Fluoride
• Nitric Oxide
• Nitrogen*
• Nitrogen Dioxide
• Ozone
• Phosgene

* A concentration limit is not included because available oxygen is the limiting factor.

Health risks associated with breathing welding fumes

According to OSHA, the Centers for Disease Control and Prevention, the International Agency for Research on Cancer, and the CNESST (Quebec), breathing welding fumes could cause the following health effects:

• Eye, nose, and throat irritation
• Dizziness and nausea
• Breathing difficulties that could lead to suffocation or asphyxiation
• Metal fume fever
• Lung damage and various types of cancer
• Stomach ulcers
• Kidney damage
• Nervous system damage
• Manganism
• Chest pain
• Asthma
• Bleedings
• Dermatitis or eczema
• Kidney disease
• Bone and joint disorders
• Siderosis (iron oxide in lung tissue after inhalation)
• Stannosis (tin oxide in lung tissue after inhalation)
• Anthracosis (poisoning after inhalation of carbon dust)
• Berylliosis (poisoning after inhalation of beryllium dust)
• Accumulation of fluid in the lungs

These are good reasons to protect welders, meet the standards, and even extract pollutants as efficiently as possible. Welding fume extractors will be the best way to do so.

To learn more about welding fume regulations in another Canadian province or territory, feel free to use one of the links below to be directed to our article on the subject:

• Alberta
• British Columbia
• Manitoba
• Newfoundland and Labrador
• New Brunswick
• Northwest Territories
• Nova Scotia
• Nunavut
• Prince Edward Island
• Quebec
• Saskatchewan
• Yukon