The Silent Killer in Your Home
Carbon monoxide (CO) is called the "silent killer" for good reason: it's colorless, odorless, and tasteless. You can't see it, smell it, or taste it — but at high concentrations, it can be fatal within minutes.
The Centers for Disease Control reports that more than 400 Americans die from unintentional CO poisoning each year, with thousands more hospitalized. Faulty heating systems and blocked chimneys are among the leading causes.
How Your Chimney Can Cause CO Poisoning
Your chimney's job is to safely vent combustion gases — including carbon monoxide — out of your home. When the chimney is blocked, damaged, or improperly maintained, those gases can back-draft into your living space.
Common causes of chimney-related CO problems include:
Animal nests: Birds, squirrels, and raccoons frequently nest in unused San Antonio chimneys during the summer months. A nest can completely block the flue, causing CO to back-draft into your home when you light your first fire of the season.
Creosote buildup: Heavy creosote deposits narrow the flue opening, restricting airflow and causing incomplete combustion — which produces more CO.
Cracked or deteriorated flue liner: A damaged liner allows combustion gases to seep into the chimney structure and potentially into adjacent living spaces.
Negative pressure: Modern, energy-efficient homes are tightly sealed, which can create negative air pressure that draws combustion gases back into the home rather than up the chimney.
Warning Signs of CO Problems
- Headaches, dizziness, or nausea when using your fireplace
- Yellow or orange flames instead of blue (for gas fireplaces)
- Excessive condensation on windows when the fireplace is in use
- Soot or black marks around the fireplace opening
- CO detector alarm activation
If your CO detector sounds, leave your home immediately and call 911.
Prevention: Annual Chimney Inspection
The most effective way to prevent chimney-related CO poisoning is an annual chimney inspection and cleaning. A CSIA-certified technician will:
- Remove any animal nests or blockages
- Clear creosote buildup
- Inspect the flue liner for cracks or damage
- Check the damper for proper operation
- Verify that the chimney is drawing properly
In San Antonio, where chimneys sit unused for 6–8 months of the year, this annual inspection is especially critical.
CO Detectors Are Not Enough
While CO detectors are essential (every San Antonio home should have them on every level), they are a last line of defense — not a substitute for proper chimney maintenance. By the time your detector sounds, CO levels are already dangerous.
Call Sweeppy at (210) 418-9810 to schedule your annual chimney inspection. We serve all of San Antonio and surrounding areas. First-time customers save $50.
