Cold temperatures, and attempts to combat them, led to two carbon monoxide poisonings last week.

On Wednesday, a man lost consciousness in a greenhouse at Panzer Nursery in Aloha. The nursery had been using 15 natural-gas heaters to keep the plants warm in the sub-freezing temperatures, but snow build-up kept the units from venting properly.

On Friday, a Hillsboro family of four all went to Providence Medical Center in Portland after inhaling excessive amounts of carbon monoxide. Hillsboro Fire reports said the chimney’s damper was closed, which might have caused the family’s Tualatin Valley Highway home to fill up with the gas.

Fire crews found a 13-year-old boy unconscious. His mother and her other two kids were suffering from headaches, nausea and other side-effects. All are expected to recover, fire officials said.

Known as the “silent kiler,” carbon monoxide is an odorless, colorless gas that results from the incomplete combustion of any material, including wood in a fireplace or woodstove. If a fire or woodstove isn’t properly vented, carbon monoxide can build up to the point where the home’s occupants are breathing that gas instead of oxygen.

As carbon monoxide replaces oxygen in the bloodstream, the victim suffers headaches, body aches, dizziness and nausea. More severe symptoms include visual disturbances, poor judgment, seizures, unconsciousness, cardiac arrest, coma and, ultimately, death.

Just before Thanksgiving in 2002, a young couple died in their Hillsboro apartment after not letting a fireplace fire vent properly. TVFR officials say that agency has responded to four carbon monoxide calls in the last five years: Three people died and seven others were taken to hospitals after those incidents.

In this recent Hillsboro case, “the mother did all the right things to assure the safety of the family,” said Connie King, Hillsboro Fire spokeswoman, in a press release. “If a person suspects that there is a carbon monoxide problem, have everybody immediately leave the home and call 9-1-1. We would much rather find a home with normal levels of CO than find people who are unconscious because they waited too long to report a problem.”

To prevent carbon monoxide poisonings:

Make sure your fireplace and/or woodstove are properly vented. Don’t close the damper until 72 hours after the fire has gone out. “Ashes and coals from a fire that has apparently ‘gone out’ can stay hot long enough to fill a home with carbon monoxide,” said Ray Eufemia, Hillsboro Fire investigator, in a press release.

Don’t use other fuel-burning appliances, like barbecues, propane grills propane or kerosene heaters, inside the home.

Keep the garage door up while your car is running.

Make sure other appliances, like furnaces and water heaters, are in proper working condition.

For more information, call your local fire department.