A fire close to an air quality monitoring station on Wednesday caused a spike in the data collected.
A concerned resident sent CBC News a screenshot of an app that tracks air quality and showed it in the 10+ range, which is "very high risk," according to Air Quality Ontario.
The data between 6 a.m. and 9 a.m., then again from 2 p.m. to 5 p.m. is no longer on the Air Quality Ontario monitoring website.
Lindsay Davidson of the Ministry of the Environment, Conservation and Parks said staff took note when the Kitchener monitoring station measured high concentrations of fine particulate matter.
Staff went to the site of the Kitchener station to calibrate the instruments used to measure air quality and also check for a potential source for the particulate matter.
"The high PM2.5 concentrations were likely the result of a fire in the area, very close to the air monitoring station," Davidson said.
He said those readings from Wednesday were "invalidated" and removed from the website "as they were not representative of regional air quality for the Kitchener-Waterloo air quality forecast region."
He also noted the app used by the person who sent CBC News the screengrab "is not affiliated with, nor endorsed by" the ministry and instead, suggested people visit the ministry's air quality website for real time information.
The Kitchener Fire Department confirmed there was an apartment fire on Brybeck Crescent which could have affected air quality in the area. The fire was caused by unattended cooking in an apartment building.