Calgary's fire chief says most of the serious fires that crews have responded to recently were caused by the careless disposal of cigarettes or other smoking materials.

Steve Dongworth held a media availability on Monday in an effort to get the message out that it's dangerous to put out cigarettes in flower pots and planters.

"Our investigators are quite shocked by how many people who are unaware of the risk that that presents," he said

"You put that butt in that planter, it smolders for a while — it takes quite a while to actually combust fully. The person goes back into their home and the next thing they know, their house is on fire."

Calgary Fire Department Chief Steve Dongworth held a news conference Monday to remind Calgarians to dispose of cigarettes carefully. (CBC)

May was the department's busiest month in five years for building and structure fires in Calgary. That month saw 46 building and structure fires, leading to $8.5 million in property losses. That amount may rise as more investigations are completed. So far in June there have been 17 blazes affecting structures or homes.

Dongworth says that of the 17 most serious fires under investigation from May and June, 10 have been determined to be caused by careless disposal of smoking material.

One of those fires was a four-alarm blaze in May that affected 200 residents of a large condo complex in Inglewood. Investigators believe a carelessly disposed cigarette in an outdoor planter on a patio sparked that fire.

"Never put out cigarettes or smoking materials in plant pots, peat moss, your lawn or your garden," Dongworth said.

"Use a deep, wide, sturdy metal container filled part way with sand or water, that should be emptied regularly."

Calgary Firefighters respond to a house fire in Martindale on June 4. (Mike Symington/CBC)

Dongworth also reiterated the importance of smoke alarms.

"No residence in Calgary should be without working smoke alarms, at least on every floor, and ideally in every bedroom," he said.

A fire on the weekend in Tuxedo in northeast Calgary in which one person died seems to have started in the kitchen, and there are indications that there were no smoke alarms, Dongworth said.

"The tragic fatality on the weekend underlines the importance of fire prevention in your home, especially working smoke alarms," he said.