Five people were rushed to hospital after they were exposed to carbon monoxide at their home in Calgary's Mount Royal neighbourhood early Thursday.

EMS incident response paramedics were called at about 6:40 a.m. to the 1400 block of Premier Way S.W., where they found the family members waiting outside in a vehicle.

The residents told paramedics they woke up feeling dizzy and nauseated, prompting them to leave the house and call 911.

Firefighters found carbon monoxide levels at 120 parts per million (ppm) in the upstairs and readings increased to 600 ppm in the basement, the fire department said in a release.

When readings are any higher than zero in a residence, it means there is something wrong, said Calgary Fire Department spokeswoman Carol Henke.

It's believed the carbon monoxide came from a faulty drainage system on the boiler, likely caused by cold weather.

No CO alarms in home

One teen and four adults — including a woman in her 90s — complained of minor symptoms and were taken to Rockyview hospital in stable, non-life-threatening condition.

"Carbon monoxide (CO) is a colourless, odourless gas. You cannot see, taste, or smell it; therefore, you could be affected, unknowingly," EMS said in a release.

"Even low levels of exposure can cause serious health problems."

There were no carbon monoxide alarms in the house.

The fire department said it wants to remind Calgarians they should have working carbon monoxide alarms on every level of their homes.