Beware the Stealthy Headache

Via Universal Hub: TS the EMT reports that we almost lost a building full of people in Boston to carbon monoxide poisoning:

Shortly after nine o'clock, a little girl crawled out of bed, tiptoed into the living room, and told her mother she wasn't feeling well.
A few minutes later, the girl's sister complained of a headache, too. Then the mother began to feel ill herself. Assuming they were all coming down with a bug of some kind, she picked up the phone and called 911.
[...]
Fortunately, nobody was found unconscious in an apartment. Workers from the gas company came to investigate, and apparently they located the source of the problem. The windows were opened, the building aired out, and the residents were able to return to their homes.
This could have been a real catastrophe. A few hours later, everyone would have been alseep. The rising carbon monoxide levels would have gone unnoticed. Dozens of people would have lapsed into unconsciousness, and by the time anyone noticed a problem, everyone in the building might have been dead.
In fact, this might have been a criminal negligence case in the making. Leaving the scene we heard talk that work was being done on the building, and that workers had temporarily disconnected the smoke- and carbon-dioxide detectors.