A three-day-long smog warning that has swept across Montreal other parts of Quebec is now in effect in Gatineau, Environment Canada said Tuesday.

Residents can expect poor air quality with high concentrations of fine particulates in the air through Tuesday evening.

Wood heating seems to be the culprit behind the cold weather smog, which is why people living in Montreal have been told for the past three days not to use their wood-burning stoves or fireplaces until the warning is lifted.

Children with asthma and people with respiratory problems or heart disease are also advised to avoid intense physical activity outside.

The warning also includes parts of the Laurentians, Montérégie, Lanaudière, Mauricie and Quebec City regions.

It's not surprising when gas and electric heating is so expensive. —@kims__opinion

Super smoggy yesterday in Montreal, warnings there <a href="https://t.co/15IxdDwm6h">pic.twitter.com/15IxdDwm6h</a> —@AD613

Despite Gatineau being just across the river, the warning does not affect Ottawa.

The reason: Quebec and Ontario use different programs to measure air quality, which means different criteria need to be met before a warning is issued, according to Environment Canada.

Meteorologist Peter Kimbell said in an interview that smog warnings this late in the year aren't that uncommon in Quebec, since many people there use wood-burning stoves.

Environment Canada said residents can help reduce the risk of smog.

"We can all help improve air quality by doing simple things, such as limiting the use of fireplaces and wood-burning stoves, opting to use public transit, reducing our driving speed and not letting our car engines idle unnecessarily," the weather agency said in a weather bulletin on Tuesday.