Carbon Monoxide Leak Kills Five, Injures Two in Missouri Duplex

Five people are dead and two others are hospitalized after a carbon monoxide leak filled a residential duplex in Phelps County, Missouri, early Friday morning. First responders arrived at a duplex on the 13000 block of Village Circle at around 5:30 a.m. and found all five victims in a single unit, according to KSDK-TV.
One survivor from the affected unit is in critical condition. A resident in the adjoining unit was also sickened with moderate symptoms. One sheriff's deputy was treated at the scene for CO exposure during the rescue, according to FOX 2 News St. Louis.
A 911 call came in at 5:24 a.m. reporting a carbon monoxide alert and unresponsive people, according to KSDK-TV. Firefighters and deputies arrived within minutes. They found high CO levels inside and immediately began pulling victims out. By 6:45 a.m., air ambulances had flown two survivors to a trauma center and a hyperbaric facility — a specialized chamber used to treat CO poisoning.
Investigators from the Missouri State Highway Patrol's Division of Fire Safety arrived by 10:00 a.m. to inspect the structure. Coroners from both Phelps and Crawford counties were also called in. The Phelps County Sheriff's Office said the investigation aims to determine the exact circumstances of the leak, according to KCTV5.
Early findings point to a heating system failure as the likely cause, though investigators have not yet confirmed the source. Carbon monoxide is colorless and odorless. It is impossible to detect without an alarm. The CDC says CO poisoning kills about 400 Americans every year in non-fire incidents. In enclosed spaces, levels above 250 parts per million can be fatal over a prolonged period, according to WFSB.
In a duplex, a leak in one unit can spread through shared crawlspaces or ventilation gaps. That likely explains why the neighbor in the adjoining unit also showed symptoms, according to safety experts. Investigators will also look at whether any CO detectors were present in the home — and whether they worked.
Missouri is the only state in the U.S. with no law requiring carbon monoxide detectors in rental properties, according to a review of state statutes by the National Conference of State Legislatures. Older homes in unincorporated Phelps County fall into a legal gap. Landlords are not required to install or maintain CO alarms. A working detector costs as little as $20.
Housing advocates say this incident was preventable. Phelps County Coroner Ernie Coverdell oversaw a similar death in March 2025, when a man and his dog died after using a generator indoors following a storm, according to KSDK-TV. State lawmakers are already signaling a push to pass a new carbon monoxide safety law in the next legislative session.
The names of the five victims have not been released. The Phelps County Sheriff's Office said it is working to notify families before making identifications public, according to WIBW. The sheriff's office described the process as "lengthy and thorough." No timeline has been given for when the full investigation will conclude.
Investigators will focus on two key questions: what caused the heating system to fail, and whether any CO detectors were ever installed in the unit. Testimony from the two survivors could be critical. Prior complaints about smells or headaches — early warning signs of CO exposure — could shape any future civil or criminal liability for the property owner.
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