A carbon monoxide leak forced dozens of residents of The Statesman apartment building to evacuate Sunday afternoon after residents called 911 due to personal carbon monoxide sensors detecting elevated levels.

D.C. Fire and Emergency Medical Services officials said pressure washing in the building’s parking garage likely produced the leak due to the use of the gas in an unventilated area, and the chemical spread upward through the apartment complex’s floors. Dozens of residents evacuated the building after receiving a notification from their carbon monoxide detectors or hearing about the leak from neighbors, but residents said they did not receive orders from The Statesman or fire officials to leave their apartments.

Officials detected normal carbon monoxide levels and allowed residents to return to their apartments about an hour after FEMS personnel arrived at the building, according to a tweet from the department.

Vito Maggiolo, a public information officer for D.C. FEMS, said firefighters detected 250 parts per million of carbon monoxide in the building’s parking garage – significantly higher than the normal range between 0.5 to 5 parts per million. He said firefighters began knocking on residents’ doors to tell them to evacuate the building after detecting elevated levels of carbon monoxide throughout the building.

“Carbon monoxide is a colorless, odorless gas that we call the silent killer because people don’t know it’s there,” he said. “The best line of defense against CO is for people to have carbon monoxide alarms in their homes or in their apartments.”

Maggiolo said officials received a 911 call concerning elevated carbon monoxide levels and possible sick residents, but did not find any residents with illness. He said FEMS personnel were working to ventilate the building and take readings of the levels of carbon monoxide.

“We’re also got some high powered fans working to provide ventilation,” Maggiolo said. “And that’s currently the state of affairs right now.”

The Statesman did not immediately return a request to comment.

Natalie Pertz, a resident of The Statesman, said she called 911 after hearing her carbon monoxide alarm go off for a second time in her apartment. She said she originally smelled a “distinct” smell and heard her carbon monoxide alarm go off for the first time after returning from leaving the building 35 minutes earlier.

“I immediately ran up to the front desk, and the woman at the front desk said that they were cleaning in the parking garage of the building, and that we should all just open our windows and it would be fine,” Pertz said. “And I decided to call 911 and saw another resident who had already gotten his pets out. And as soon as I call 911, they said yes, ‘This is going off, you should evacuate and there could be poison in the building.’”

Pertz said she viewed the building’s response to the situation as “unacceptable” and she would be looking into ways to hold The Statesman accountable.

“The most disturbing part of all of this is none of us were notified at all ahead of time to evacuate, to open our windows, none of that,” Pertz said. “I am going to investigate what else can be done here to hold the building accountable because this is unacceptable and dangerous and who’s to say if there aren’t some other residents whose pets are in there right now because the residents are out, it’s a busy weekend for GW students, it’s a period of transition, so I’m going to be investigating what else can be done here.”

Kiera Fyffe, a senior studying political science, said she left her apartment to walk her dog and discovered the firetrucks and evacuated residents outside, but was not aware of the leak prior to leaving the building.

“There are no alarm or anything,” Fyffe said. “I walked down and I saw people outside and firefighters and kind of asked around to see what’s happening.”

Bridget Perry, a senior majoring in journalism and Statesman resident, said she decided to evacuate the building after learning that other residents of the building were evacuating. She said she originally saw the fire trucks and ambulances from her window but assumed that they were responding to a situation at the building next door because she did not hear an alarm going off on her floor.

“I packed up my cat in his little carrier, and I left because I just wasn’t sure what was going on,” Perry said.

Dan Wilken, a GW Law student, learned of the gas leak when waking up to go get food and walked outside to the sight of the D.C. FEMS personnel surrounding the building. He said he went for a walk around the area because he didn’t know exactly what happened, and came back to the building after seeing a D.C. FEMS tweet that said it was okay to return.

“I didn’t hear anything from The Statesman but D.C. Fire has a Twitter thing, so they said that it was fine and people who were waiting around told me it was fine, but they haven’t said anything really,” Wilken said.

Nick Pasion, Isha Trivedi and Zach Blackburn contributed reporting.