USI Plug In CO & Natural Gas Alarm

Isn’t natural gas (essentially methane) lighter than air and, thus, will rise above the outlet that this thing would be plugged into? Just askin’…

My AC guy that installed my gas furnace said we had a gas leak and that we should have a CO/Gas detector, this seems like a good price and I can put it in the hall under where my furnace is in the attic.

Amazon Reviews pretty thin, mentions “design flaw”. Meh, seems like this is a pretty common design and is better than nothing.

I totally read that as “UFO Plug In CO & Natural Gas Alarm” and thought to myself: You know, I really could use a UFO alarm.

Alas it was not to be.

will this detect propane?

Why would I ever need this??? I already know if I cut the cheese. I don’t need a detector that tattles on me and says that I was the one who created some natural gas. I’d rather no one know so I can blame someone else.

Thanks for deleting the spam.

May need extension cord.

There are more reviews on more appropriate websites that give this a consistent positive review.

Beware: This must plug in to an outlet (or ugly extension cord) that is very near, or in, the ceiling. I bet your house doesn’t have a receptacle up there. If you place it low, it will likely not detect a problem until too late: CO rises slowly, but if propelled by warm (burned) smoke of course it rises faster. Natural gas also rises.

Yup. I was just going to post this.

If you want this to protect while you’re sleeping consider the level your head is at in bed, and the level the sensor is on the wall.

Probably below your head.

Carbon Monoxide is also approximately the same weight as air, but if it is combined with warm air it will generally rise to the top of the room.

So, Natural Gas and Carbon Monoxide are both likely to fill the room from the top down, and if the sensor is below your head you’re likely to be effected before the sensor goes off.

If it did detect propane it really would do no good. Propane is heavier than air and would be at ground level. (assuming the gas detector was in the ceiling area)

Kidde recommends that if your gas is Propane, you mount their unit low; but if you use natural gas, please mount it high.

It is a design flaw if the design encourages the average user to use the device incorrectly.

It may not have a technical sensing flaw, but one thing you have to always take into account is the user. Most users would probably take the direct plug design and plug into a standard low wall outlet.

That review is pretty concerning. People have copied and pasted bits and pieces but here’s the full thing for you to read.

**WARNING! Dangerous design flaw!


THIS PRODUCT MUST BE PLUGGED DIRECTLY INTO AN OUTLET - THERE IS NO POWER CORD.** This is a major design flaw that can lead to ineffective detection of carbon monoxide and/or natural gas. Here is why this is a problem…

Natural gas is much lighter than air. This means that in an enclosed space filled with air, such as a room in your home, natural gas will rise to the ceiling. It will displace the breathable air from the top of the room down. Unless it is located within inches of the source, the alarm will not sound until natural gas fills the space from the ceiling down to the level of the alarm. As I stated, this alarm MUST be plugged into an outlet. The outlets in most every home are placed 12-16 inches from the floor. If placed in this position, the alarm likely will not sound until after the air at breathing level has been displaced to non-life sustaining levels. Basically, it will not go off until AFTER you are unconscious! The alarm must be placed at ceiling level (or at least higher than where your head rests in bed) in order to afford protection!

In addition, serious injury or death from a natural gas leak may not only occur from direct exposure, but also as a result of an explosion. Proper placement (ceiling level) of the alarm will increase the likelihood that the alarm will sound before the gas reaches an ignition source. However, due to the design flaw, proper placement is not possible unless you have an electrical outlet at ceiling level.

The placement of a carbon monoxide alarm should also be high in the room as CO is also lighter than air. CO is only slightly lighter, however, so it tends to mix some with air as it displaces oxygen. If placed in a standard outlet, the alarm will be more likely to detect CO than natural gas, but it far from ideal.

I spoke with the company about my concerns, but they would only say “our product is manufactured to UL specifications”. I’m sure this is true. It’s also irrelevant. I have no doubts this alarm will detect CO and natural gas. However, the design flaw means it will not be in a position to detect that gas in a timely manner.*

It’s okay to pinch penny’s on vacuum’s and computers. But when i’m counting on something to save my life I’ll spend the extra 20 bucks and buy a product that doesn’t suck. Think about it, Is this something you really want to skimp on?

Anyone else wanna copy pasta from Amazon?

This should be able to detect both propane and methane, but at different sensitivities. Sensor is probably set to Methane, but will detect most other combustibles too.

Probably has a low end catalytic bead sensor for that.

As far as placement, I’m not finding anything definitive. Although CO is slightly lighter than air, most sources I found didn’t think this would be much of an effect, with only a slight difference in concentrations between the floor and ceiling. Not a “3 feet between life and death!!” thing.

One thing to note is that placement directions for CO and gas detectors vary. CO detectors should be near bedrooms so they’ll jolt you awake. They also get a better reading of the CO where you’re sleeping.

Gas detectors should be near gas-using appliances, like in the kitchen. By the time the gas level is elevated enough to detect near your bedroom, it could be explosive in the kitchen.

So you can’t really place them where both functions will be useful. A CO detector in the kitchen is prone to false alarms.

We have a First Alert combo smoke/CO detector in the kitchen and have never had a false alarm. The smoke detection is photoelectric, which is less prone to false kitchen triggers than ionization sensors. And well-functioning kitchen appliances shouldn’t emit CO or anything similar to CO, so there shouldn’t be any false CO alerts either.

That may not be completely true. A false sense of security may be worse than no security at all. For example, having this installed may prevent one from exploring other options, i.e. a battery operated or hardwired model that can be placed high.

I don’t agree.

Gases follow the ideal gas law regardless of their identity
Gases mix to form homogeneous solutions regardless of their identity.

lighter gases diffuse faster than heavier gases because their molecules are moving faster

The lighter gas molecules will diffuse faster throughout the container (room). Even if the gas detector is placed toward the bottom of a room - it won’t matter, lighter gases diffuse faster- and hence will be throughout the room high and low in equal amounts.

  1. At what height/location should a CO device be mounted?
    According to the National Fire Protection Association (NFPA 720), the location for effective performance is not generally dependent on mounting height. The density of carbon monoxide is similar to that of air at room temperature, and carbon monoxide generally mixes readily with air. The manufacturer’s installation instruction should also be followed.