By Marcelle Dibrell

Carbon monoxide causes more than 400 deaths and over 100,000 emergency department visits each year in the United States, according to the Centers for Disease Control and Prevention.

Yet, the agency states, “CO poisoning is entirely preventable.”

Incidents continue to show how easily it goes undetected — even in structures that meet local building codes.

In 2023, four people — including a 3-year-old — were hospitalized after carbon monoxide accumulated in an indoor pool area at a hotel in Rochester, Minnesota. The source was a gas-fired pool heater. Detectors were installed in required locations, but not in the pool enclosure. Exposure went unnoticed until occupants became ill.

Carbon monoxide alarms are common in homes, apartments, and hotels, but their placement is driven by code requirements that vary by occupancy and conditions — not consistently by how carbon monoxide behaves. Alarms may be required near sleeping areas or when fuel-burning appliances are present, but not necessarily where carbon monoxide is generated or where it

https://www.chlorine.org/pool-interlock-safety/ accumulates. When failures occur, it is often because carbon monoxide can move beyond the areas covered by those requirements.

There is a gap between where carbon monoxide is produced, where it accumulates, and where alarms are required. Often, these do not align.

This is not a technical failure.

It is a structural one.

Most state laws require carbon monoxide alarms only under specific conditions — such as new construction, property transfer, or the presence of certain equipment — according to the National Conference of State Legislatures. Protection depends on classification and timing, not simply risk.

Roughly half of U.S. states have explicit carbon monoxide alarm statutes, while many others rely on building codes or conditional requirements rather than universal mandates.

In Kansas, for example, requirements are limited to certain lodging occupancies and do not extend broadly to all residential buildings. In Missouri, there is no single statewide code, and requirements are often adopted locally. Hawaii is often cited as lacking a comprehensive statewide mandate for carbon monoxide detection in homes. States such as Indiana rely on building code triggers, leaving many existing homes outside requirements. Even in states with broader laws — including California, New York, and Illinois — alarms are typically required near sleeping areas, not at equipment locations.

Pool and spa environments make the problem easier to see. Gaslost fired heaters are often located in enclosed or semi-enclosed spaces — mechanical rooms, pool enclosures, or exterior equipment areas — that may not be classified as occupied, even though people may be nearby or share air with those spaces. Investigations show the same pattern: Carbon monoxide is generated at the equipment, then migrates into occupied areas.

A widely reported fatal case in Niles, Michigan, in 2017 illustrates a different type of failure. Carbon monoxide from a malfunctioning pool heater accumulated in the hotel’s indoor pool area and spread into adjacent spaces, killing a 13-year-old boy and sending more than 10 others to the hospital. Investigators found that there was no carbon monoxide detector in the pool area where the gas accumulated, and because the hotel was an older builder, it was not required under state law to have one at that time.

In many jurisdictions, carbon monoxide requirements for hotels apply primarily to new construction or major renovations, leaving older buildings outside the scope of those rules — and unprotected.

Meanwhile, model codes from the National Fire Protection Association and International Code Council generally require alarms near sleeping areas — not at the source. In Rochester, detection was present where required, but not where exposure occurred. In Niles, that gap left the hotel outside the scope of the law at the time.

A building can meet code and still lack detection where carbon monoxide is ultimately present — whether at the source or where it accumulates. Pool systems do not create this problem; they make it obvious.

Smoke alarms followed a different path. They began appearing in homes in the late 1960s and were built into codes through the 1970s and 1980s. Over time, requirements expanded to include existing homes, rentals, and nearly all residential occupancies. Public education, insurance incentives, and enforcement made them standard. Today, smoke alarms are not just required — they are assumed.

Carbon monoxide alarms entered codes decades later, largely in the 1990s and 2000s, and remain tied to conditions. They have not reached the same level of consistency or expectation as smoke alarms.

That gap has begun to shift responsibility to occupants. Medical and safety organizations, including the National Carbon Monoxide Awareness Association, now advise travelers to bring portable carbon monoxide detectors with them when they are staying in unfamiliar accommodations. No one travels with a smoke alarm — that protection is assumed. Carbon monoxide protection is not.

Like smoke alarms, carbon monoxide detection requirements have developed through state laws and code adoption — not a national standard. Federal efforts have been limited. The Safe Stay Act — introduced in 2020 and reintroduced by Representatives Angie Craig and Mike Levin — would require detectors in hotels and short-term rentals, but it has not passed. Proposals often stall, reflecting state control over building codes and ongoing debates over cost and scope.

The system is not unregulated — it is conditional. Detection exists. Codes exist. Requirements exist. But carbon monoxide detection is not treated as a baseline safety feature. It is applied selectively, not expected universally. Smoke alarms became universal because they were treated as essential. Carbon monoxide alarms have not reached that point.

Until carbon monoxide detection is treated the same way — universal, expected, and non-negotiable — carbon monoxide illnesses and deaths will continue.