In 2009, several tour buses parked close to ventilation shaft at an ice arena (during a major tournament) in Illinois caused an evacuation and sent several individuals to a hospital
Link: I was officiating a game then. I thought I was coming down with the flu in the worst way.
CO can be highly insidious as far as how it builds up. Here’s one frightening example of how easily this can occur. In recent years there has been a big move to have houses more and more airtight to reduce energy costs. I believe that almost all new gas furnaces have a dedicated air supply pipe that goes to the outdoors to bring in combustion air (this isn’t the case everywhere but I believe it is with all new furnaces where I live)… so furnaces usually aren’t the problem. However, the furnace isn’t the only combustion air source in the house…. one device which is often overlooked but typically should be of far greater concern is the water heater. If a gas water heater is used that is naturally vented (as opposed to having a fan to discharge the flue gases, there is a very real likelihood that the flue gas could end up in the house if conditions change in the house that cause the indoor air pressure to drop below outdoor ambient. How could that happen? Very easily….. take a house that has been built quite airtight and now turn on some equipment that exhausts air. A few years ago, I bought a high powered hood arrangement for my kitchen that has a fan on that exhausts air at the rate of 350 cubic feet per minute. Switch that on and switch on a few bathroom exhaust fans… and for good measure, do some vacuuming with a central vac unit that is located and exhausting into the garage. All of a sudden, you might find that your house has gone quite negative and if that naturally aspirated gas fired water heater comes on at that time, it very likely will be discharging its fumes into the indoor space because it can’t vent against the air that is entering your house via the gas water heater flue pipe. If this happens to coincide with your teenage daughter having an hour long shower and someone doing a pile of laundry, that water heater could be on for a very long time… There are plenty of documented cases where this is the exact mechanism where people living in their houses have been poisoned.