The incident happened at an apartment complex at 205 West Touhy Avenue. Park Ridge Fire department responded after residents became sick.
Firefighters found high levels of carbon monoxide in the basement and cleared the building.
"We were freaking out at first, and I went to the hallway and alarms were going off," resident Mikey Achramowicz said. "People were coming out their doors so it didn't seem like just a drill, so we came outside. Slowly figuring out the situation, but it seems to be pretty serious."
Residents said the basement was being pressure washed and that's where firefighters found the leak.
A mobile ventilation unit was brought in to clear the toxic gas.
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Symptoms
The most common symptoms of carbon monoxide poisoning are headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion, according to the CDC.
Reducing risk
To reduce your risk of carbon on monoxide illness, the CDC recommends installing battery-operated detectors near bedrooms.
The CDC recommends detectors with a digital readout because they usually include an alarm.
Carbon monoxide detectors should be replaced every five years. Replace batteries every spring and fall to make sure they are working.
To read more about carbon monoxide poisoning symptoms and risks, click here.