Is your furnace as dangerous as mine?

[SSquared]

I did a similar test on my trailer today, a 2013 25FB. I visited the trailer in its storage area (an open shed) and set up a CO2 monitor and a particle monitor. I let the trailer sit empty for a few minutes, then re-entered and turned on the furnace. I then went outside and watched the values on the meters.

Unfortunately, the furnace outside vent was not completely clear at first (due to how I had the trailer stored); I cleared it after about 15 minutes. In those first 15 minutes, the CO2 increased by about 75 ppm but the PM values did not change. Once I cleared the vent, the PM values increased steadily. In the next half hour, PM 1, 2.5, and 10 reached 48, 69, and 75 respectively. CO2 actually dropped 20ppm during this time.

At that point, I fired up an air filter, and the PM values dropped steadily. In 35 minutes, they were down to 16, 32, and 40.

I turned off the furnace and left the filter running. The PM values got down to zero in another half hour, and the CO dropped about 50ppm.

What does this mean? Well, some CO2 is getting in, but not a lot. The PM is concerning, but there is no way to know if the particles are from combustion or dust in the ducts. The PM values are not as bad as what rufusd7 saw.

This does make me want to run the air filter box whenever we run the furnace.

One other data point: before I started, my trailer's CO meter had a recorded max reading of 17ppm. I cleared that, and after the test, the max was zero.

It would be interesting to run the test again, but with the vents open. We normally keep both our small bathroom vents wide open, and our two fantastic vents open at least an inch, just to keep the inside air fresh. My test was run with all vents and windows closed.


Coincidentally, last month I made an appointment to have the furnace serviced. It has an intermittent issue getting started (in humid low altitude conditions). I also am having them inspect the heat exchanger. This trailer has seen a lot of furnace use and I want to be sure it is still good. (we have camped over 1500 nights in this trailer, often in rather cool conditions).

[uncle_bob]

Originally Posted by rufusd7

Exploring this further: We may have a design flaw. The furnace literature explicitly says that the ducts must be rated for 200 degrees F or better. Most plastic ducts I have seen are only rated to 180 degrees F. I haven't had a chance to check the make/brand of the ducts in my unit, but if not rated for these temps, it could be a fire hazard in addition to a health issue.

Hi

You can most certainly get > 200 degree plastics. If the furnace folks want that, I'd bet there are ducts made out of those plastics.

Given how this is proceeding, I would suggest selling the trailer. It sounds like you have convinced yourself that there is a problem and it is bugging you to death. I would not replace it with any trailer or boat out there. You will have the same sort of concerns on all of them Indeed if you dig into the typical rental vacation cottage, you will have the same sort of concerns ....

Bob

[Tim A.]

Originally Posted by uncle_bob

Given how this is proceeding, I would suggest selling the trailer. It sounds like you have convinced yourself that there is a problem and it is bugging you to death. I would not replace it with any trailer or boat out there.

I agree.

Tim

[rufusd7]

Originally Posted by SSquared

I did a similar test on my trailer today, a 2013 25FB. I visited the trailer in its storage area (an open shed) and set up a CO2 monitor and a particle monitor. I let the trailer sit empty for a few minutes, then re-entered and turned on the furnace. I then went outside and watched the values on the meters.

Unfortunately, the furnace outside vent was not completely clear at first (due to how I had the trailer stored); I cleared it after about 15 minutes. In those first 15 minutes, the CO2 increased by about 75 ppm but the PM values did not change. Once I cleared the vent, the PM values increased steadily. In the next half hour, PM 1, 2.5, and 10 reached 48, 69, and 75 respectively. CO2 actually dropped 20ppm during this time.

At that point, I fired up an air filter, and the PM values dropped steadily. In 35 minutes, they were down to 16, 32, and 40.

I turned off the furnace and left the filter running. The PM values got down to zero in another half hour, and the CO dropped about 50ppm.

What does this mean? Well, some CO2 is getting in, but not a lot. The PM is concerning, but there is no way to know if the particles are from combustion or dust in the ducts. The PM values are not as bad as what rufusd7 saw.

This does make me want to run the air filter box whenever we run the furnace.

One other data point: before I started, my trailer's CO meter had a recorded max reading of 17ppm. I cleared that, and after the test, the max was zero.

It would be interesting to run the test again, but with the vents open. We normally keep both our small bathroom vents wide open, and our two fantastic vents open at least an inch, just to keep the inside air fresh. My test was run with all vents and windows closed.


Coincidentally, last month I made an appointment to have the furnace serviced. It has an intermittent issue getting started (in humid low altitude conditions). I also am having them inspect the heat exchanger. This trailer has seen a lot of furnace use and I want to be sure it is still good. (we have camped over 1500 nights in this trailer, often in rather cool conditions).

Thank you so much for this data point! I am glad your numbers are lower.


I find it concerning that the filters doesn't eventually clear *all* the PM. To me that means a source of PM is being brought into the trailer.

[rufusd7]

I brought the AS into a dealer. Airstream central recommended to the dealer bubble and pressure leak tests on the propane lines. These turned up nothing.

I will try to withhold comment on the wisdom of recommending such tests and, when just those test passed, declaring nothing wrong given the data.


This week, I will have the AS back along with some high-quality ($$$) furnace testing equipment that I have coming in. I will report the results.

I have ruled out, for now, the duct work itself because the ducts used are rated to 230 degrees F while the furnace requires a rating of only 200 degrees F. (A possibility that remains is that the furnace actually exceeds 230 due to insufficient air flow.)

[rufusd7]

Originally Posted by uncle_bob

Hi

You can most certainly get > 200 degree plastics. If the furnace folks want that, I'd bet there are ducts made out of those plastics.

Given how this is proceeding, I would suggest selling the trailer. It sounds like you have convinced yourself that there is a problem and it is bugging you to death. I would not replace it with any trailer or boat out there. You will have the same sort of concerns on all of them Indeed if you dig into the typical rental vacation cottage, you will have the same sort of concerns ....

Bob

See the update. Airstream did actually use the correctly spec'ed duct work. I looked at the duct work since the particulate count actually increased faster over time possibly as if something was charring.

The data shows a problem that any reasonable person should be concerned about. It's a problem that should not exist (Dometic agrees with this). For context, the last time I saw air quality this bad was during the Canada fires when you could actually see the smoke in the air. The PM quantity is about what you would see if someone was smoking in a closed up trailer.

I don't agree that people who care about clean air shouldn't own RVs, especially since we know how to design RVs that don't do this.




Edit: Note also that Airstream markets its RVs as having healthier air than other RV brands wrt VOCs.

PM 2.5 has been repeatedly linked to lung cancer, COPD, Asthma, Interstitial lung diseases, and TB.

[rufusd7]

Another update.

I tested the idea that the duct work is dirty. Running ONLY the fan for 15 minutes by turning the propane off resulted in PM1.0, 2.5, and 10 of 0 (nada) for all three (using 3 different test instruments). Never even moved the needle.

I tested the idea that the CO alarm would go off if flue gas was making its way into the trailer by measuring the furnace exhaust outside. The furnace exhaust contains 0 PPM CO. That never moved. This makes sense. If burning propane always created CO, then using the stove would set off the CO alarm.

Interestingly, I noticed that the PM does not go up immediately. This could mean two things (I welcome other ideas):

1. A faulty furnace in which enough heat opens up an otherwise sealed combustion chamber. This happens because metals expand when heated.

2. A part of the system is breaking down when too hot. For example, the duct work is rated to a certain temperature. Inadequate airflow at the furnace can air that is hotter than that rating.

I am open to ideas here.


Question: From where does the furnace return air come from in the 27FB 2022 Flying Cloud?

[uncle_bob]

Originally Posted by rufusd7

Another update.

I tested the idea that the duct work is dirty. Running ONLY the fan for 15 minutes by turning the propane off resulted in PM1.0, 2.5, and 10 of 0 (nada) for all three (using 3 different test instruments). Never even moved the needle.

I tested the idea that the CO alarm would go off if flue gas was making its way into the trailer by measuring the furnace exhaust outside. The furnace exhaust contains 0 PPM CO. That never moved. This makes sense. If burning propane always created CO, then using the stove would set off the CO alarm.

Interestingly, I noticed that the PM does not go up immediately. This could mean two things (I welcome other ideas):

1. A faulty furnace in which enough heat opens up an otherwise sealed combustion chamber. This happens because metals expand when heated.

2. A part of the system is breaking down when too hot. For example, the duct work is rated to a certain temperature. Inadequate airflow at the furnace can air that is hotter than that rating.

I am open to ideas here.


Question: From where does the furnace return air come from in the 27FB 2022 Flying Cloud?

Hi

If combustion does *not* produce CO then the CO you are finding must be magical in some way. There is no other process in a furnace that can or would produce CO. Getting things hot can produce various chemical "problems" CO is not one of them ....

Bob

[rufusd7]

Originally Posted by uncle_bob

Hi

If combustion does *not* produce CO then the CO you are finding must be magical in some way. There is no other process in a furnace that can or would produce CO. Getting things hot can produce various chemical "problems" CO is not one of them ....

Bob

I never said that I found CO anywhere. There is no CO anywhere I measured: none in exhaust gas, none from stovetop, none in trailer. Rather, I am responding to peopke (and airstream) who say that because I find no CO, there is not a problem.

[CBWELL]

CO is produced by POOR COMBUSTION!! Good combustion produces NO CO!! If you are having all this problem with the air quality in your trailer, test other trailers and see if they have the same problem. If they do, then, you must decide if you want to take the chance of living and breathing the air in the trailer. I have never heard of this problem before, as most others on this site have not as well. If you are really concerned, the trailer shoud be taken to a Certified Lab for testing.

[rufusd7]

These results pretty much speak for themselves. It appears that the "duct tape" that AS used on my unit is not rated for these temperatures. It looks like it is pretty much just burning off over time. I will fix and report. I wonder how many others are impacted.


https://www.mrhandyman.com/blog/2016...on-your-ducts/
"Duct Tape Can Be a Fire Hazard"

[Genebuilder]

Don’t stand too close to the furnace while you are doing all this exotic testing. I don’t think your underwear is rated for “those temperatures” either.

[10Smiles]

Nicely done rufusd7. It looks like you've narrowed it down. I must have missed it, what is the significance of 160 degrees? I see that the PM goes up at this temperature, but is there a reason other than that that you picked it?

[rufusd7]

Originally Posted by 10Smiles

Nicely done rufusd7. It looks like you've narrowed it down. I must have missed it, what is the significance of 160 degrees? I see that the PM goes up at this temperature, but is there a reason other than that that you picked it?

Thank you. I started with where the PM started and ended (on the yellow line) and looked for relationships with all the data I collected (temp of AS, temp at other outlets, etc.). 160 on the hottest outlet was the only thing that consistently matched the start and stop of the PM generation.

[rufusd7]

Originally Posted by Genebuilder

Don’t stand too close to the furnace while you are doing all this exotic testing. I don’t think your underwear is rated for “those temperatures” either.

True! Looks like cotton is only good to 150F. Good thing I was not in the AS during any of the tests. It was all done remotely thanks to a RaspberryPI.