An accidental gas leak in a Texas apartment building has sent a dozen residents to the hospital with carbon monoxide poisoning, according to ABC News. One person was found unconscious after the leak, and 12 patients in total were sent to hospital after the building was evacuated, with residents complaining of "nausea, vomiting and severe headaches," Houston Fire Department District Chief Raul Villasana told KHOU-TV.

The leak took place in Gessner apartment blocks in southwest Houston and is believed to have originated from a vent serving dryers in the complex which then caused carbon monoxide to flow into nearby apartments, according to NBC News.  

An Oregon couple, Kendra Platt and Steven Roberts, were among the residents affected by the leak and were reported by WBT to have been enjoying an uneventful night in when they started to feel the effects of the leak. Roberts complained of feeling sick in the evening and then remained woozy the next morning, eventually leading to him passing out, according to WBT.

"I knew something serious had happened, but not sure what," Roberts told WBT, with Platt adding that "if I passed out we both would have been dead right now."

After calling 911, the couple was taken to a nearby hospital and treated in a hyperbaric chamber to restore their oxygen levels to normal, according to ABC. Officials reported on Sunday night that all patients affected by the leak were now OK, according to WBT.

Exposure to carbon monoxide is highly dangerous, with the Centers for Disease Control and Prevention reporting it as the cause of around 430 deaths per year. Symptoms include headaches, dizziness and vomiting, and can in extreme cases be fatal. Experts recommend that you keep a working carbon monoxide detector in your home to avoid undetected risks.