An elderly Calgary couple has diedand nine others were sentto hospital Wednesdayin an apparently accidental case of carbon-monoxide poisoningcaused by acar left running in the northwest home's garage.

The couple'sson andeight emergency workers were also exposed to the deadly gas in the home, Calgary fire department spokesman Jeff Budai said.The son is listed in hospital in serious but non-life-threatening condition.

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Police say a car was left running in the home's attached garage. ((CBC))

Firefightersand paramedics responded to a 911 call by the son around 5:30 p.m.MT Wednesday after he found his father unconscious.

When paramedics and firefighters arrived, they foundthe elderly man in cardiac arrest and not breathing. His son told themhe didn't know where his mother was.

Crews searched the house anddiscovered the mother, whowasalso in cardiac arrest.

The fire captain also noticed unusual behaviour from the son, who "was staggering a little bit," Budai said.

"He made the decision to pull everyone from the house."

The levels of carbon monoxide inside the home were so high thatfour firefighters, two police officers and twoEMS workers started getting sick.

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Eight emergency workers were taken to the hospital after getting sick with carbon monoxide poisoning.

All are expectedto recover, saidemergency measures spokesmanPaul Lapointe. The couple, who were in their 70s,died in the hospital.

Neighbour Christina Switzer, who lives with her boyfriend across the street from the couple's home, told CBC News thatshe sawemergency workers discover a running car in the garage.

"They opened the garage door and found that the car was running and more ambulances came," Switzer said. "It was really scary."

In all, 12 EMS units were sent to the scene, Lapointesaid.

"When our own staff are involved — whether it be paramedics, firefighters or police — it's a pretty frightening situation to be in," he said.

"It just increases the stress levels, but we treated this call like we wouldany other call."