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The Houston Fire Department reprimanded a firefighter for misconduct after an investigation into a delayed 911 response to a case in which a mother and daughter died of carbon monoxide poisoning.

The department opened the investigation in July, following reporting from ProPublica, The Texas Tribune and NBC News, which revealed that first responders initially decided not to enter a Houston family’s home during the massive winter storm that hit Texas in February 2021, a decision that resulted in a couple and their two children being exposed to the lethal gas for an additional three hours.

The fire department has not disclosed details of the investigation. In a letter to the Texas attorney general fighting the release of records to the news organizations, Houston officials wrote that state law prevents the public disclosure of records dealing with misconduct of a firefighter or police officer. But the letter states that the “allegations of misconduct in this investigation were sustained and disciplinary action was taken against the firefighter.”

In an email to the news organizations, Houston Fire Chief Samuel Peña confirmed that the investigation found evidence of misconduct but declined to elaborate because of a potential appeal from the disciplined firefighter. Peña told the news organizations in August that he was awaiting the results of the investigation but that it appeared a fire captain in the dispatch center “failed to provide the necessary information for the people on scene to make the appropriate decision.”

The department’s decision to discipline a firefighter is one in a series of actions taken by governmental bodies after a yearlong investigation by the news organizations, which found failures at every level of government to protect residents of Texas and other states from carbon monoxide poisoning. Safety gaps and a lack of consistent policies have left residents vulnerable to the invisible gas. These policy failures contributed to the worst carbon monoxide poisoning catastrophe in recent history as power outages swept Texas during the winter storm, the news organizations found. The state has confirmed at least 19 deaths from carbon monoxide after residents tried to stay warm by using barbecue grills, running their cars or starting up portable generators in enclosed spaces.

Following reporting on the dangers of portable generators and the lack of federal regulations, the U.S. Consumer Product Safety Commission last week announced that it intends to recommend new mandatory rules to make the generators safer, saying manufacturers have not voluntarily done enough to prevent carbon monoxide poisoning deaths caused by their products.

And in Texas, the Harris County fire marshal is drafting a proposal that would require carbon monoxide detectors in more apartments and town houses, at the request of county commissioners. Harris County leaders also said they would lobby the Legislature during its next session in 2023 for the ability to require carbon monoxide alarms in single-family homes.

The decisions came after the news organizations found that Texas was one of only six states with no statewide requirement for carbon monoxide detectors in homes, resulting in uneven protections for residents. The Texas Legislature later passed a measure that requires carbon monoxide alarms in homes built or renovated starting this year. The legislation does not apply to nearly 10 million existing homes and apartments.

Harris County, which includes Houston, was hit particularly hard by the 2021 storm. At least five people died from carbon monoxide poisoning, and more than 590 residents sought care in emergency rooms after exposure to the gas.

Shalemu Bekele, his wife, Etenesh Mersha, and their two children were among those poisoned on Feb. 15, 2021, after she turned on their car that morning in the family’s attached garage to keep warm and charge her phone. Relatives called 911 in the evening after they were contacted by a friend who had been on the phone with Mersha when she and the family stopped responding.

Firefighters were dispatched to the home but left after no one answered the door. A 911 dispatcher told Michael Negussie, Bekele’s cousin, that he would relay concerns that the family might have been poisoned by carbon monoxide to the emergency responders on the scene, but never did, according to 911 recordings and records obtained by the news organizations, as well as interviews with fire department officials.

A fire crew returned nearly three hours later after a series of increasingly worried 911 calls from Negussie, who repeatedly told dispatchers that he believed his relatives had been poisoned. The emergency responders entered through an unlocked door and found Mersha and the couple’s 7-year-old daughter, Rakaeb, dead. Bekele and their 8-year-old son, Beimnet, were rushed to the hospital, where they recovered.

Neither Negussie nor Bekele responded to requests for comment this week.

Because of a lack of uniform policies, first responders in Texas and across the country have discretion when deciding whether to enter a home. Houston fire officials have pointed to a department memo that says firefighters should ensure that they are in the right location, look for signs someone is inside, check with neighbors and contact dispatch to ask for additional information from the caller. If emergency crews decide to forcefully enter the home, they should call the police for support, according to the memo.

Officials with the city’s fire department did not respond to questions about whether they had made any policy changes following the investigation into the circumstances of Mersha and Rakaeb’s deaths.

Bill Toon, a retired EMS provider and consultant with decades of experience, said the department should assess whether additional policies are needed to prevent future incidents.

“To me, this isn’t about an individual — it’s about a systemwide practice,” Toon said. “If you’ve discovered this incident, and it probably isn’t the only one that they have, what are you going to do to prevent it from happening in the future?”