Heat can kill you. So can the air you breathe.

And in extreme cases, so can a neighbor who snaps because his air conditioner conks out during a sweltering heat wave.

For those who don't have air conditioning coping with an infernal heat wave means either staying inside and sweating to death or venturing outside and succumbing to the smog that usually accompanies these extreme temperatures.

Higher night-time temperatures means there's no relief, even when the sun goes down. For an increasing number of people heat waves means a trip to a hospital emergency ward in search of relief.

Dr. Jean Zigby, who runs a community health clinic in Montreal is on the front lines in the war against heat prostration.

But Zigby may be fighting a losing battle because heat waves, once rare in this country, have become more and more the norm each summer. Last year during a 10-day period of a protracted heat wave Zigby treated more than 35 patients for heat stroke.

People with any sort of respiratory illnesses are most at risk, says the affable 31-year-old physician who not only teaches his patients how to stay cool in intense heat waves, but is also working to make his community health centre as environmentally friendly as possible.

"Immune compromised children with respiratory problems, the elderly with respiratory problems, grandmothers and grandchildren are basically the ones in the family who are going to be paying for all this," said Zigby. "The poor are going to be the ones who pay first. The people who can less adapt to these types of changes. People who don't have access to air conditioning."

Air conditioners are the necessary evils and the power pigs of a modern society. Greenhouse gases produced by human activity are derived mostly from industrial development especially the internal combustion engines and coal burning electric power generators.

"We teach our elderly patients stay well hydrated, keep their homes well ventilated and as cool as possible, and to make sure they are not isolated during periods of heat stress," said Zigby adding that people with cardiovascular illnesses are especially at risk.

Those who work in emergency rooms see first hand the most obvious health implication of climate warming and the increase in the ambient temperature.

Heat waves are also associated with the occasional outbreaks of violent and antisocial behavior. Studies show that people become more aggressive and irritable when exposed to high temperatures.

Active in environmental issues since his days in high school, Zigby who was born and raised in Quebec's Eastern Townships before moving to Montreal 12 years ago, is striving to make his Community Health Centre the most environmentally friendly in the country. It is a model he hopes will be copied and implemented by other community health centers across Canada.

"We are looking at everything from the electricity we use the garbage we produce," Zigby said in a recent interview. "We've just completed a waste audit to look into ways of cutting back and we're systematically trying to either reduce it, reuse it or recycle it."

Energy efficiency is a must whether it is turning out lights to making sure all the equipment in the clinic is as energy efficient as it can be. Zigby is also trying to reduce or a number of toxins, including mercury and lead, from his day-to-day practice.

A graduate of McGill medical school, and a member the Canadian Association of Physicians for the Environment (CAPE) Zigby became active in environmental issues during high school, but took a break from activism while he pursued his studies.

He owes it to his family, especially his young daughter, Juliette, 3, to try and make a difference.

"I'm worried that I'm going to have my daughter in 10 years from now looking at me and saying," Dad why didn't you do anything? We knew it was coming, we had all the information, why didn't you do something?"

So, are we in this country likely to see a killer heat wave the likes of that which hit France last year that left an estimated 15,000 people dead?

"It is possible? I guess anything is possible," Zigby said. "Is it likely? I wouldn't go as far as to say it is. But those of us who are keeping track of changes in the climate are always looking out for something like that."

Zigby is one of the heroes featured in the Great Warming, a three-hour documentary narrated by Alanis Morrissette and Keanu Reaves.

Filmed in eight countries on four continents and endorsed by dozens of the world's leading scientists, this visually stunning series premiers on the Discovery Channel on, Earth Day, April 23.