UL 2201 vs PGMA G300: What Generator CO Safety Standards Actually Require

Why these standards exist

Portable generators produce carbon monoxide at very high rates, and CO is colorless and odorless. The U.S. Consumer Product Safety Commission (CPSC) estimates that portable generators are associated with an average of nearly 80 CO poisoning deaths per year. Many victims ran generators in garages, basements, or near open windows during outages.

The CPSC began rulemaking on portable generator CO hazards in 2016. While that process continued, two industry groups published voluntary standards with CO hazard mitigation requirements in 2018: UL published a new edition of UL 2201, and the Portable Generator Manufacturers' Association (PGMA) published ANSI/PGMA G300. Both have since been updated, and CPSC's 2026 safety messaging refers to the 2023 editions.

PGMA G300: shutoff-focused

ANSI/PGMA G300 is a broad safety and performance standard for portable generators. Its CO requirements center on a CO shutoff system: a sensor that turns the generator off when carbon monoxide around it reaches specified levels. The standard also requires that the CO sensor used in the shutoff system carry a UL mark or equivalent mark from a nationally recognized testing laboratory, and it includes tamper-resistance requirements for the shutoff system.

What G300 does not do is require the engine to emit less CO in the first place. The generator can produce CO at conventional rates, relying on the shutoff to stop it when levels climb.

UL 2201: emissions plus shutoff

UL 2201 addresses the problem from two sides. It limits the CO emission rate of the generator, which means the engine itself must produce much less carbon monoxide. It also requires shutoff at specified CO concentrations. In CPSC's analysis of the standard, UL 2201's weighted emission rate limit was 150 grams per hour, with shutoff at 150 ppm as a rolling 10-minute average or 400 ppm instantaneously.

Reduced emissions matter because CO builds up more slowly around a low-emission generator. That buys time before levels become dangerous, including in situations where a shutoff might not react fast enough to protect people nearby.

How CPSC evaluated them

CPSC staff ran more than 140,000 simulations based on 511 portable generator fatalities in CPSC databases, modeling different house types, generator locations, and weather conditions. The staff found:

• Generators compliant with UL 2201 would avert nearly 100 percent of the deaths studied.
• Generators compliant with PGMA G300 would avert about 87 percent.

CPSC concluded that UL 2201's combination of reduced emissions and shutoff was more effective than G300's shutoff-only approach. At the time of that 2022 report, CPSC staff also found that compliance with UL 2201 was minimal and compliance with G300, while greater, was lacking for many models on the market. Compliance with G300 has grown since, and industry groups say most portable generators now include CO shutoff technology.

Where the federal rule stands

CPSC proposed a mandatory safety standard for portable generators in 2016, then published a supplemental notice of proposed rulemaking in 2023 that built on the voluntary standards. The supplemental proposal found that UL 2201's emission and shutoff requirements were highly effective in simulation, while noting that a shutoff system must be durable and reliable in real-world conditions, which is where some of G300's construction and tamper-resistance requirements come in.

As of our most recent check, a final mandatory rule has not been issued. Industry groups have opposed a mandatory rule, arguing that voluntary compliance has grown and that G300's shutoff approach is highly effective. Check CPSC's website for current status before relying on any summary, including this one.

What this means when you shop

1. Look for the standard name on the packaging or specifications, not just a brand feature name.
2. Prefer UL 2201 when available, because it adds reduced emissions.
3. PGMA G300 is still a major improvement over generators without any CO protection.
4. Neither standard makes indoor use safe. Generators must always run outdoors, far from the home.

See our list of the best generators with CO shutoff for shopping guidance, and our CO shutoff safety guide for broader safety practices.

The layered approach

No single safeguard is perfect. The most protective setup combines:

• Placement: outdoors, far from the house.
• A generator with CO shutoff, ideally UL 2201.
• CO alarms inside on every level and outside sleeping areas.
• Awareness: everyone in the household knows the symptoms of CO poisoning, including headache, dizziness, weakness, nausea, confusion, and sleepiness.

Reading a spec sheet

When you look at a generator listing, the CO safety information might appear in a few places: the feature bullets, the specifications table, the packaging, or the owner's manual. Useful phrases include "complies with ANSI/PGMA G300," "certified to UL 2201," or a listing mark from a testing laboratory. Vague phrases like "CO safety technology" without a named standard are not enough to tell you which requirements the generator meets. If the listing is unclear, check the manufacturer's website or contact support before buying.

Why emissions matter even with a shutoff

A shutoff reacts after carbon monoxide has already accumulated. In a small, enclosed space, CO can rise quickly, and people nearby may already be affected before the sensor trips. Lower emissions slow that buildup. That is why CPSC staff found the combination in UL 2201 more protective, and why placement outdoors, far from the house, remains the single most important safety practice regardless of certification.