Colorado Springs, CO – The wood burning stove used to warm a Lamar woman’s house recently almost killed her — all because it emitted an odorless, colorless and deadly gas.

She hasn’t been alone.

Memorial Hospital Central, which has the state’s only 24-hour hyperbaric chamber center, has seen a spike of carbon monoxide-related admissions since mid-December, said Dr. Rob Price, medical director of the hospital’s hyperbaric department.

Thirteen people from across southern Colorado, including the Lamar woman and a few people from Colorado Springs, have been treated since Dec. 15 at the hospital, Price said.

A handful of those patients were sickened by wood burning stoves, he said. Others were poisoned by furnaces that did not function properly — causing carbon monoxide to fill their homes.

The spike in cases has illustrated the importance of installing carbon monoxide alarms in each room of a house, Price said. The Lamar woman never installed the device, he said, and she only realized her house was filling with carbon monoxide when her body started seizing, he said.

She received treatment inside one of the hospital’s three chambers, which are filled and pressurized with 100-percent oxygen to purge the toxin from the body.

“Carbon monoxide alarms are a must,” Price said.

Carbon monoxide is often called a “silent killer” by public health officials, because it has no color and no odor. It has been known to kill people in their sleep — first causing drowsiness and then suffocation.

The severity of each case depends on the concentration of the gas, and each affected person’s health.

In low concentrations, the gas can cause fatigue and flu-like symptoms, according to El Paso County Public Health.

Symptoms at higher concentrations include headache, dizziness, weakness, vomiting, chest pain, confusion and loss of consciousness.

From 2004 through 2014, 30 people in El Paso County were hospitalized for carbon monoxide poisoning, said Danielle Oller, a spokeswoman for the county agency. They were among 283 carbon monoxide-related hospitalizations across the state during that time.

Such poisonings typically happen during cold-weather months, when Coloradans are more likely to use appliances that emit the gas, such as faulty furnaces.

For example, calls to Colorado Springs Utilities about the gas double during cold-weather months, said Steve Berry, a utilities spokesman. Every year, Colorado Springs Utilities receives about 1,800 calls concerning carbon monoxide, he said.

Memorial Hospital only treated one person over the summer for carbon monoxide poisoning, Price said. In the fall and early winter, the hospital averaged two to three cases a month.

In minor cases, patients can be treated with an oxygen mask. However, in more severe poisonings, patients are treated by spending up to three, two-hour sessions inside the hyperbaric chamber, Price said.

Prevention is key, Price said.

He stressed having furnaces inspected each year, changing furnace filters annually and making sure chimneys are clean and clear of obstructions, to keep the gas from building up.