CO detector is good where heating system is. Also one in hallway outside of bedrooms.
What I’m asking is: I understand there’s circulation, but I have no way of measuring it. If the circulation is minimal – that is, some air is able to exit the room, because it’s clearly not airtight – is there still ENOUGH circulation of air that I don’t need to worry about the oxygen in the room being used up. The heating vent in the room is pretty small, not a lot of flow needed to heat that small of an area (we’re in LA… it doesn’t get THAT cold here).
I know, it sounds paranoid. But I have no way of measuring the oxygen levels or circulation levels. I’m assuming physical harm is a long shot, but I’m just trying to find an objective way of figuring this out. Again, it’s not just the air pressure on the door, it’s the significant heat difference in the space. Heat is being trapped there, air escape is at least limited.
So either there’s enough air circulation that I really don’t need to give it a second thought, or the circulation is so limited that over time, there can be a drop in oxygen levels and an increase in carbon dioxide from 2 people sleeping in the room. I don’t know what the minimum circulation required is, nor how to measure it here.
If heat is coming into the room from the register there is circulation. Air cannot enter the room without air leaving. When the furnace is running, put your hand under the door (from outside) and you’ll probably feel a slight breeze. At least not a significant amount. Home HVAC systems just aren’t designed to pressurize rooms to any real extent beyond that little bit of pressure you’re feeling on the door. Since we know there is circulation, you can be comfortable knowing that the O2 level in that room is the same as it is in the rest of the house.
The key is that it is really hard to fight the iron will of those gas particles. The O[sub]2[/sub] concentration outside the room is 21%, and if the concentration inside deviates, O[sub]2[/sub] will find its way in or out to compensate.
How about some rough numbers…
Let’s say you had to push with 10 pounds of force to get the door cracked open. If the door is 2 m[sup]2[/sup] in area, then that means the room is over-pressured at 0.003 psi (on top of the ambient 15 psi). Since air was still coming in through the vent, then that means the room cannot hold a pressure difference greater than 0.003 psi.
Imagine the O[sub]2[/sub] concentration dropped from 21% to 20.8% – a biologically negligible difference. This corresponds to a change in oxygen (partial) pressure of (15 psi) * (0.002) = 0.03 psi. This is 10 times greater than the pressure the room can apparently hold. So, the lowest the concentration can get (assuming the vent flow is turned off) is 10 times less than this change, or 21% --> 20.98%. Taking 19.5% as a tolerable lower limit, you’ve got a safety factor of, like, 75x.
Let’s pretend oxygen couldn’t get in. There is still the fresh air from the vent. In an 8 hr period, your kids together wouldn’t burn more than 1400 calories. That requires the oxygen contained in about 4000 L of air. That sounds like a lot, but it corresponds to only 0.3 cfm of air flow (cubic feet per minute). A typical bedroom vent might be putting out 200 cfm. That’s a safety factor of 600x.
So, even if my numbers are off by a factor of 2 or 5 or 20, you’d still be perfectly fine. There are certainly caveats to the above that could make me off by 10x or so (e.g., the balance of inward diffusion against the outflowing air), but even still – you could put your kids on treadmills in the middle of the room all night, and they’d be fine.
You know, I had breakfast with a rocket scientist the other day. I’m glad there are folks like him – and you guys – around to set us lunk heads straight. =)
Thanks for letting me (and the kids) sleep easy!