False positives on carbon monoxide detector could be something even worse

ST. LOUIS COUNTY, Mo. – When the carbon monoxide (CO) detector wouldn’t stop going off at a Town & Country home, the owner tried everything, including paying to have a security company switch out alarms.

The CO readings continued. Firefighters responded. It wasn’t carbon monoxide, but something possibly worse.

“My best guess would be is that it would be more like a natural gas type of explosion,” said Dep. Chief Kelly Grassmuck, West County EMS & Fire. “It’s going to light off. It’s going to burn that gas. It is going to cause an explosion. It’s going to cause some damage and it could ultimately result in a sustainable fire that catches your house on fire.”

Turns out there was a buildup of hydrogen gas from the area around the sump pump. The 12v battery backup that keeps the pump running if there’s a power outage was out of water and started “cooking.”

“It was cooking down. When it does that it ‘off-gases.’ … sulfur and hydrogen gas,” Grassmuck said.

The hydrogen buildup can reach explosive levels within just a few hours, especially in closed-off areas where sump pumps tend to be.

Luckily, hydrogen gas can create a false positive reading on a CO detector.

Your best line of defense is to check water levels on battery backups at least every couple of months, Grassmuck said.

You can also buy a backup system that will warn you when the battery is low on water. They run about $150 at home stores.

If you have concerns, call your fire department. Like carbon monoxide, you can’t see or smell hydrogen, and it doesn’t have to explode to kill you.

“Especially in a closed room like that, you’re not only walking into a room that’s loaded with hydrogen gas that is explosive, you’re also walking into an oxygen deprived atmosphere. So if something happened in there and you pass out, your chances of survival are probably pretty slim,” Grassmuck said.

Improving ventilation also helps. Use distilled water when filling batteries.

This is a concern anywhere 12v batteries are routinely charged, for forklifts, for example.