The welding fume limit is on the whole fume, and four metal limits in the same list sit above it

What the brackets mean

“Not otherwise classified” reads like a residual category: the fume left over once the named metals are accounted for. It is not. The evaluation report Safe Work Australia commissioned to set the standard states its scope in one line: the term welding fumes (NOC) refers to the total fume produced as a result of welding processes.

That is the whole fume, whatever is in it. The recommendation itself is equally plain: It is recommended that the Workplace Exposure Standard for welding fumes (NOC) be 1mg/m3 (based on the inhalable fraction). The limits list published in November 2025 carries that number.

Australia was offered the other approach and turned it down

Several countries dropped a total welding fume limit and now rely on limits for the individual metals instead. The report considered that and rejected it, in terms worth reading in full if you are deciding what to monitor:

This approach is not recommended for Australia because the harmful constituents of welding fumes are not known in their entirety. The reason given is the basis of the cancer classification itself: The IARC designation of welding fumes as a human carcinogen was based on total welding fumes, not on any specific component of welding fumes.

And the practical consequence, which is the sentence a duty holder should take away: Focussing only on the individual constituents runs the risk of not measuring the presence of a relevant constituent or combination of constituents and thus underestimating the relevant exposure of workers.

The four that sit above it

The same published list that sets welding fume at 1 mg/m3 sets separate limits for individual metals as fume. Four of them are higher than the total welding fume limit. Every figure here is the eight-hour time-weighted average, read from the November 2025 list.

Zinc oxide also carries a short term exposure limit of 10 mg/m3. Cobalt is listed as metal and inorganic compounds at 0.02 rather than as a fume, so it is left out here. Non-metal fume entries in the same list include ammonium chloride at 10, paraffin wax at 2 and bitumen fumes at 0.5.

Read together with the definition above, the arithmetic is the point. A welding process producing mostly zinc oxide fume reaches the total welding fume limit at 1 mg/m3, while the zinc oxide entry does not bite until 2. The limits are set on different things, and the one on the whole fume is the tighter of the two.

What the report says about its own number

It is unusually candid, and reporting it fairly matters because it is the basis of a limit that binds. The recommendation is not derived from a dose-response relationship: There is insufficient published information to confidently propose either a health-based or risk-based Workplace Exposure Standard for welding fumes (NOC). The justification given is that Safe Work Australia had already lowered the standard from 5 mg/m3 to 1, that comparable overseas standards run from 1 to 5, and that consistency with them should err on the side of providing additional protection of workers.

The countries that went the other way did not all do so because the risk was lower. The report records that the United Kingdom withdrew its 5 mg/m3 total welding fume standard in 2005 because it was considered the limit may not be sufficiently protective of health, and that Ireland, New Zealand and the United States no longer have a formal total welding fume standard either.

The date that changes which list you are working to

The November 2025 document is the workplace exposure limits list that replaces the older workplace exposure standards. Until 30 November 2026 a PCBU must still ensure no person is exposed above the standard in the older list; after that the newer one applies. For the next two months both exist, so any figure quoted from either should say which it is.