A natural gas smell at a Saskatoon hotel ended up being a carbon monoxide leak.
It happened just before 2:45 a.m. Friday at the Saskatoon Inn on Airport Road.
The Saskatoon Fire Department said readings of 10 to 61 ppm were recorded in the seven-storey hotel.
The issue was traced to a defective heating unit on the roof and once it was shut down, carbon monoxide levels started to decrease, said the fire department.
No evacuation of the hotel was required.
Crews then started ventilating the building with fans.
Two hours into the call, additional crews were sent to relieve the initial responders.
Officials said fire trucks at the scene were at risk of freezing due to the -46 C temperature.
Ventilating operations were not interrupted during the changeover and carbon monoxide levels were down to zero just after 6 a.m.
SaskEnergy was also called to the hotel to assist fire crews.
No injuries or medical concerns were reported with any guests or staff of the hotel.