ACGIH TLVs: What They Are, Why They Matter, and What the 2025 Updates Mean for Canadian Employers

If your workplace has solvents, fuels, welding fumes, dusts, coatings, cleaning chemicals, or process emissions, there’s a good chance you’ve bumped into the acronym ACGIH TLV—or you should.

ACGIH (American Conference of Governmental Industrial Hygienists) publishes Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) as health-based guidance for controlling worker exposure to chemicals and physical agents. Importantly: TLVs/BEIs are not laws or standards—they’re guidelines used by occupational hygienists to make decisions about safe exposure levels.

ACGIH^® Board Ratifies Fall 2025 TLVs^® and BEIs^®

So why should Canadian employers care?

Because across Canada, regulators and employers frequently reference ACGIH TLVs when setting or updating occupational exposure limits—and when TLVs change, compliance expectations can shift quickly.

A timely example: WorkSafeBC publishes updates tied to new or revised ACGIH TLVs and describes how those TLVs can become B.C. Exposure Limits (ELs) through its review and board decision process.

TLVs in Plain Language: the “Speed Limits” for Exposure

A TLV is an airborne concentration a worker can be exposed to—day after day over a working lifetime—without expected adverse health effects for “nearly all workers” (with important caveats).

You’ll typically see TLVs expressed as:

• TWA (Time-Weighted Average): average over an 8-hour workday / 40-hour week
• STEL (Short-Term Exposure Limit): a 15-minute exposure limit (often referenced alongside TWAs)
• Ceiling (C): a concentration that shouldn’t be exceeded

Key CrossSafety note: TLVs are one input into risk management—not the whole story. ACGIH explicitly warns TLVs/BEIs are only one of multiple factors in evaluating real workplaces.

“TLVs Aren’t Regulations”… But They Drive Real Compliance Changes

ACGIH TLVs are developed by committees that review peer-reviewed science, and they’re health-based—ACGIH notes they don’t factor in economic or technical feasibility.

That’s exactly why TLVs can move lower over time when evidence strengthens. And when a province adopts those changes as enforceable limits, it becomes immediately relevant to your exposure control program.

BC’s approach, as an example

WorkSafeBC explains that twice a year ACGIH publishes a list of substances with new or revised TLVs, and WorkSafeBC may adopt them as B.C. Exposure Limits (ELs) (after review of health data, sampling methods, and stakeholder consultation, then a board decision).

WorkSafeBC’s January 2025 update also lists examples of substances added for review based on ACGIH’s new/revised TLVs (e.g., diacetone alcohol, heptane isomers, metribuzin, triethylene glycol).

How to Use the ACGIH “Substances & Agents Listing” Without Getting Lost

ACGIH’s listing is a living map of what’s changing, including items like:

• Notice of Intended Changes (NIC) (what may change next)
• Adoptions (what’s been adopted into TLVs)
• Under Study (what’s being actively evaluated)

ACGIH also emphasizes that users should consult the latest documentation to understand the basis for a TLV (not just the number itself).

Practical tip: If a substance you use shows up as “NIC” or “Under Study,” treat it as a heads-up to tighten monitoring and controls—before limits potentially move.

What Employers Should Do When TLVs Update

Whether your jurisdiction has formally adopted the new numbers yet or not, TLV updates are a strong signal to pressure-test your exposure control program.

Here’s a simple, high-impact checklist:

1) Re-check your chemical inventory (don’t trust last year’s list)

Look at:

• Coatings/adhesives/solvents
• Fuels and exhaust sources
• Cleaning agents
• Welding/cutting byproducts
• Dust-generating tasks (cutting, grinding, demolition)

2) Compare tasks to exposure limits that actually apply to you

Different limits may apply depending on province, industry, and substance classification. BC, for instance, uses “Exposure Limits (ELs)” terminology in its framework.

3) Validate controls in the right order

• Substitution (less hazardous products)
• Engineering (local exhaust ventilation, enclosures)
• Administrative (time limits, scheduling, housekeeping)
• PPE/respiratory protection (only when properly selected, fitted, and maintained)

4) Monitor when the risk is plausible—not only after complaints

Air monitoring and exposure assessments are especially important when:

• Processes change
• New products are introduced
• Ventilation is modified
• You see symptoms/odours/dust accumulation
• You’re relying heavily on PPE

5) Train for the “why,” not just the WHMIS checkmark

Workers should understand:

• What the exposure is
• How controls protect them
• What triggers escalation (odours, visible dust, symptoms, process changes)

CrossSafety’s Perspective: TLVs Are Your Early Warning System

TLVs aren’t just numbers in a book—they’re a science-based trendline. If TLVs are tightening for substances you use, that’s your cue to confirm you’ve got:

• The right controls,
• The right monitoring plan, and
• The documentation to prove due diligence

Exposure Limits Change. Your Program Should Keep Up.

If your team works around solvents, dusts, fumes, or other hazardous agents, CrossSafety can support your exposure control strategy—from hazard assessments and program updates to training and documentation. Explore our HSE consulting services for compliance support.