Crankcase Humidity Check Tool

[Tcheairs]

I'd like to verify whether or not my Black Max dehumidifier is working properly to dry out my crankcase on my IOX Continental 360. I found this tool on Amazon and I was wondering if this might work by sticking the probe into the oil fill tube and taking a sample.

https://www.amazon.com/Protmex-Temp...&hvlocphy=&hvtargid=pla-4584138857623079&th=1

Is there possibly a better method for testing the humidity level in a crankcase?

Thanks

 

[Dan 57]

I seem to recall that Mickey aka rv8ch did some measuring, but can't find a source right now... bet he'll chime in pretty soon

 

[Desert Rat]

I built my own dehumidifier that works via desiccant beads, but the principle of measuring the humidity in the air is the same no matter the mechanism used for drying the air.

You just need a clear airtight chamber in the air line pulling from the crankcase with a humidity gauge in it. I made mine out of a food canister from the dollar store that has an airtight lid and a couple of barbed fittings. I got the gauge on amazon. I think for that part of the mechanism including canister, fittings and gauge I spent about $20.

The measurement section is the upper part of the canister device in the first picture below. The air line pulling from the engine goes into the upper chamber where the gauge is, then out to the pump, then to the dryer chamber then back to the engine. By plumbing it this way the gauge is reading humidity in the air coming from the engine before the dryer chamber has sucked the water out of it.

I fired this up in July when it was super humid. Picture 2 shows what it was initially reading when I turned it on, picture 3 was after it was running for about 15 minutes.

 

[tgmillso]

Glass Jar with sensor inside

I found a glass jar with a small AAA battery operated room humidity sensor to work. One tube in, one out. See the second last photo in the link below:

https://vansairforce.net/community/showthread.php?t=157922&highlight=Dehumidifier

Tom.
RV-7

 

[Majorpayne317641]

I ended up going with drybot because of issues I’ve had with blackmax. The way I did it was to run an inline desiccant filter with a viewable window, the same kind you use to dry air hoses in line. I then was able to determine my unit was sending humid air into the engine as it was turning purple within a day of use sometimes. I don’t know how humid but humid enough to turn beads purple.

 

[gasman]

I'd like to verify whether or not my Black Max dehumidifier is working properly to dry out my crankcase on my IOX Continental 360. I found this tool on Amazon and I was wondering if this might work by sticking the probe into the oil fill tube and taking a sample.

https://www.amazon.com/Protmex-Temp...&hvlocphy=&hvtargid=pla-4584138857623079&th=1

Is there possibly a better method for testing the humidity level in a crankcase?

Thanks

I would try this first...... https://www.amazon.com/Hygrometer-T...fix=remote+humidity+reader,garden,247&sr=1-11

 

[dpansier]

Check out the Elitech Digital Temperature Humidity Data Logger GSP-6, works well and the probes are small allowing entry into the oil filler tube.
Mine has been in service for nearly 3 years without fault. Amazon has them listed.

 

[rv8ch]

The Black Max puts out air at 40% humidity, which is below the level that causes rust. If you put the colored beads on the output of the black max, they will pick up that moisture.

Using the beads, in a closed loop system, I was able to get the humidity down to the teens.

I spoke to Ben who produces the Black Max and he said he's creating a "tester" to allow people to monitor the output of the Black Max, since this is a frequent request.

If you want to roll your own, just put an empty bottle between the output of the black max, put a temp/humidity sensor in there, and you'll know what's going in.

I still think there is a lot of room for innovation here. My dream would be a nitrogen generator that just slowly fills the empty space in the engine with nitrogen.

Here's my current monstrosity that I'm using to compare the dessicant beads with silicon kitty litter. The kitty litter doesn't work, by the way.

Use a pair of ESP32 devices, 2 temp/humidity sensors (one ambient, one after drying), with a bit of code to read the sensors and upload the data to a google sheet which I plot in grafana.

 

[von_flyer]

I developed a dehydrator solution based on the simple approach many DYI examples seen over the years. I did testing with real data before offering it as a product. I attached the photos of some of the data I collected to confirm it was doing what it was supposed to. I equate using a dehydrator to taking vitamins, not apparent result until later in life perhaps. You don't know how well its working until you tear down the engine. The data was my 'engineering' approach to assuring it was working.

The data report with warmer temperatures was done in Florida, and the colder set of data was an example in Michigan winter. I did quite a bit of data logging to show it does work.

I have built about 100 dehydrators now and I do use the Amazon humidity and temperature meters. I sort through them as about 10-20% or them come inaccurate.

The data loggers, which I have used three independently, on the other hand are very accurate.

 

[rockwoodrv9]

I have one of Jon's dehydrators and it works great. I rejuvenate the beads about every couple months to keep the humidity under 25%. My hangar is cold in the winter and hot in the summer. In the winter here in Michigan there can be extended times that I cant fly and I want the engine to stay dry.

I developed a dehydrator solution based on the simple approach many DYI examples seen over the years. I did testing with real data before offering it as a product. I attached the photos of some of the data I collected to confirm it was doing what it was supposed to. I equate using a dehydrator to taking vitamins, not apparent result until later in life perhaps. You don't know how well its working until you tear down the engine. The data was my 'engineering' approach to assuring it was working.

The data report with warmer temperatures was done in Florida, and the colder set of data was an example in Michigan winter. I did quite a bit of data logging to show it does work.

I have built about 100 dehydrators now and I do use the Amazon humidity and temperature meters. I sort through them as about 10-20% or them come inaccurate.

The data loggers, which I have used three independently, on the other hand are very accurate.

 

[calvind]

I made one using a TI HDC1080 sensor board from Amazon - 2 for $11. It has an I2C interface so I used an ESP32 board (~$5) running a simple Arduino program to get the data and display it on a cheap character LCD. The board is mounted to a brass tee fitting with 1/8 NPTF ports.

I also made my own dehydrator using an old oxygen concentrator that was collecting dust. Removed the zeolite granules from the sieve bed cannisters and replaced with silica gel. The same pressure swing adsorption/purge cycle works with both media types and it takes care of keeping the dessicant dried out.

The RH of the discharge air measures less than 4%. It is connected to a mechanical timer that runs it for an hour every 12 hours and the air goes into the dipstick tube. I have spot checked the crankcase RH a couple times and it is consistently below 10%.

 

[rv8ch]

I made one using a TI HDC1080 sensor board from Amazon - 2 for $11. It has an I2C interface so I used an ESP32 board (~$5) running a simple Arduino program to get the data and display it on a cheap character LCD. The board is mounted to a brass tee fitting with 1/8 NPTF ports.

I also made my own dehydrator using an old oxygen concentrator that was collecting dust. Removed the zeolite granules from the sieve bed cannisters and replaced with silica gel. The same pressure swing adsorption/purge cycle works with both media types and it takes care of keeping the dessicant dried out.

The RH of the discharge air measures less than 4%. It is connected to a mechanical timer that runs it for an hour every 12 hours and the air goes into the dipstick tube. I have spot checked the crankcase RH a couple times and it is consistently below 10%.

Cal, this is very interesting - can you talk more about this solution? I love the idea of self-generating dessicant.

I have the Black Max which is fine, but from time to time it stops working and I need some replacement parts. This seems to happen about every 12 months.

I built an ugly, standard closed-loop dryer, and here's my numbers from the last two days.

 

[Tcheairs]

Mickey, what exactly do you mean by your Black Max stops working? No lights?
No fan? I get lights and the fan when I turn mine on but after it goes through a cycle, it doesn't seem to come back on and re cycle. Lights stay on however. Have you sent yours back to Black Max for inspection? if so, what did they do to your machine.

In any case, it would be nice to have a method of verifying that it is working. I'm not interested in going through the desicant machine fabrication again. Been there..done that..

Thanks from the OP

 

[Majorpayne317641]

This is exactly how the drybot works. It self recharges the dessicant, I’ve used both and prefer the drybot over the black max.

Cal, this is very interesting - can you talk more about this solution? I love the idea of self-generating dessicant.

I have the Black Max which is fine, but from time to time it stops working and I need some replacement parts. This seems to happen about every 12 months.

I built an ugly, standard closed-loop dryer, and here's my numbers from the last two days.


View attachment 53396

 

[Majorpayne317641]

Like my previous post on this, I placed an in line desiccant canister you can buy at Lowe’s. This is how I monitored if my blackmax was working, and it would turn the desiccant blue in a day when it was not working properly when I was testing its effectiveness.

Mickey, what exactly do you mean by your Black Max stops working? No lights?
No fan? I get lights and the fan when I turn mine on but after it goes through a cycle, it doesn't seem to come back on and re cycle. Lights stay on however. Have you sent yours back to Black Max for inspection? if so, what did they do to your machine.

In any case, it would be nice to have a method of verifying that it is working. I'm not interested in going through the desicant machine fabrication again. Been there..done that..

Thanks from the OP

 

[BillL]

Check out the Elitech Digital Temperature Humidity Data Logger GSP-6, works well and the probes are small allowing entry into the oil filler tube.
Mine has been in service for nearly 3 years without fault. Amazon has them listed.

+1

I just ordered my second one. The good thing about this is it claims to read down to 10%RH, but goes even lower - - may not be accurate lower than 10% but does not stop there.

Highly recommended. Note though: the battery is $6-10 for replacement but my first one has lasted 3 yrs and still shows a full charge. It is a data logger too, 16000 points. That is a lot of minutes.

BTW - - A Peltier condensing cooler can not (Blackmax?) go much below 32F dew point - therefore I have abandoned that for my next generation dryer. I am now using a new desiccant - and it yields RH well below 10% at 30F, it measured < 2% at 45F, That is a very low DP. Testing continues.

 

[rv8ch]

Mickey, what exactly do you mean by your Black Max stops working? No lights?
No fan? I get lights and the fan when I turn mine on but after it goes through a cycle, it doesn't seem to come back on and re cycle. Lights stay on however. Have you sent yours back to Black Max for inspection? if so, what did they do to your machine.

In any case, it would be nice to have a method of verifying that it is working. I'm not interested in going through the desicant machine fabrication again. Been there..done that..

Thanks from the OP

The main failure part in the black max is the "cooling block" - it's a fan and Peltier unit, and some sensors. When it fails, it causes one of the lights to flash and the pump and fans to stop. Then you have to contact the supplier. I've replaced a couple of cooling blocks, and the wiring skills I learned working on my RV-8 have served me well here. Shipping the whoie unit back from Europe to be repaired is not cost effective, so Ben just sends me the cooling block. It seems that the latest design is much more reliable, so hopefully this block will run for many years.

Here's a picture of the guts:

 

[calvind]

Mickey-
The concentrator I used was a Devilbiss Devo 44 (5 lpm I think). Inside there are two cannisters about 18" long and 3" in diameter, oriented vertically. The end caps have 1/4 NPT bosses in them and are crimped to the main tubes. Not knowing what I would find inside I cut off both caps on each cannister. Inside there are perforated plates and fiber mats to contain the granules but allow gasses to pass through. At the top end of each cannister there is also a spring between the end cap and the perf plate that serves to keep the granule bed tightly packed. As it turned out it would only have been necessary to remove the top caps.

Once the caps were off it was a simple matter to remove the perf plates and empty out the zeolite granules. Then I made some aluminum replacement end plugs with O-ring grooves that can be slipped inside the main tubes and secured with screws while the o-ring provides the seal. They are threaded 1/4 NPT to match the original caps. The new silica gel dessicant came from a supplier on ebay ($23 for 5 lb). It took most of that to fill the two cannisters.

At any moment during the cycle there is one active cannister dehumidifying the air while the other cannister is being purged. Valves and a control board route compressed air to the bottom of the active cannister while the other one is being vented to the atmosphere (also at the bottom). A second valve at the top directs air flow from the active cannister to the output storage tank and from there through a relief valve to the output port. The relief valve is set to crack at about 28psi and this determines the pressure in the storage tank and active cannister. Meanwhile an adjustable bleed valve connects the tops of the two tanks so that a little bit of the discharge air from the active cannister bleeds into the top of the one being purged to help flush out the humid air. In my unit the role reversal happens about every 15 seconds.

The control board senses pressure at a couple points in the system in order to detect malfunctions and I had to fiddle with the bleed valve setting as well as the output flow to get the unit to run reliably with the new media.

Concentrators with the normal zeolite sieve beds also deliver really dry outlet gas but it seems just wrong to use a gas that is over 90% oxygen for the purpose of preventing oxidation, regardless of how dry it is!

 

[Tcheairs]

I’m gonna buy one. How do I contact John?

 

[BillL]

Brilliant adaptation . . .

Mickey-
The concentrator I used was a Devilbiss Devo 44 (5 lpm I think). Inside there are two cannisters about 18" long and 3" in diameter, oriented vertically.

The new silica gel dessicant came from a supplier on ebay ($23 for 5 lb). It took most of that to fill the two cannisters.

Concentrators with the normal zeolite sieve beds also deliver really dry outlet gas but it seems just wrong to use a gas that is over 90% oxygen for the purpose of preventing oxidation, regardless of how dry it is!

Silica gel does not make a good PSA desiccant but it does clearly work. Since you have the system, Carbon Molecular Sieve CMS220 may work to concentrate atmo to nitrogen. I am making a PSA (don't have an old oxygen concentrator :-() from scratch and using 5A molecular sieve beads for the dryer. Just replacing my silica gel with the 5A improved cold performance from 23% RH to 1.5% RH with a 80%RH@37F input stream. The 5A can be regenerated up to 500F - a lot higher than silica gel. My reason for seeking improvement is when the ambient is low and the silica gel bed is not fresh. It has the possibility an equilibrium state that would release water to the stream rather than reducing it.

I'll be on the look out for an abandoned O2 concentrator too!

 

[rockwoodrv9]

Here are a couple pictures of the amount of moisture just after an oil change and then a short trip to get fuel. My oil only got to 140 degrees so no chance to burn it off but I was surprised at how much water vapor came out of new oil.

I have the Mojave system and it is showing 11% humidity inside the engine after spiking up to 34% just after shutdown. It took about 20 minutes to reduce to the 11%. I leave it running 24-7.

I have the AntiSplat oil plug heater and I also use a small amazon heater ducted into my inlet to make sure the top of the engine warms up too. It was in the 20's last night and I turned on the Amazon heater only at about 11:30. When I got to the airport this morning the oil was 94 degrees and the carb was 104. I know it wont be enough when it gets colder here but I was surprised it heated the entire engine that well. The AS oil plug will do the same and Im sure I will need both here shortly!!

 

[Tcheairs]

Rockwood, which Amazon heater do you use plugged into the intakes? I'm using a 400w ceramic heater ducted to the Vetterman exhaust tubes, but I'm only able to ger 70-80 degrees throughout the engine block. Also, I am hearing in this forum that (low) heat on the engine during storage actually accelerates moisture buildup inside the engine..comments?

 

[rv8ch]

Silica gel does not make a good PSA desiccant but it does clearly work. Since you have the system, Carbon Molecular Sieve CMS220 may work to concentrate atmo to nitrogen. I am making a PSA (don't have an old oxygen concentrator :-() from scratch and using 5A molecular sieve beads for the dryer. Just replacing my silica gel with the 5A improved cold performance from 23% RH to 1.5% RH with a 80%RH@37F input stream. The 5A can be regenerated up to 500F - a lot higher than silica gel. My reason for seeking improvement is when the ambient is low and the silica gel bed is not fresh. It has the possibility an equilibrium state that would release water to the stream rather than reducing it.

I'll be on the look out for an abandoned O2 concentrator too!

This looks like an abandoned project, but there are some good videos with some hints here that we might be able to use to build our better mousetrap.

https://www.youtube.com/@projectoxygenator4562/videos

I think if there is a way to use Oxygen Concentrator technology to extract Nitrogen instead of Oxygen, that would be one of the best gasses to inject into an engine to reduce corrosion.

 

[rockwoodrv9]

Rockwood, which Amazon heater do you use plugged into the intakes? I'm using a 400w ceramic heater ducted to the Vetterman exhaust tubes, but I'm only able to ger 70-80 degrees throughout the engine block. Also, I am hearing in this forum that (low) heat on the engine during storage actually accelerates moisture buildup inside the engine..comments?

Im not sure how heating the engine to 80-100 degrees and pumping 10% moisture air through it can cause accelerated moisture but if it does, I would like to know.

Heater I am using. Amazon Basics 500-Watt Ceramic Small Space Personal Mini Heater - White. It is about $25.

I never thought about ducting through the exhaust tubes. Interesting idea. I had the AntiSplat oil heater prototype so I normally use it and then thought I would like to heat the top of the engine at the same time so I added the small ceramic heater. I have a 5"x5" to 3" round transition duct fitting and it goes right into my inlet. I have a piece of about 3/8" aluminum foam insulation I put over the duct to the cowl sealing most air leaks and holding everything in place. I use the Switcheon system to control everything and it works great for those with crappy cell service.

 

[Dean Pichon]

Rockwood, which Amazon heater do you use plugged into the intakes? I'm using a 400w ceramic heater ducted to the Vetterman exhaust tubes, but I'm only able to ger 70-80 degrees throughout the engine block. Also, I am hearing in this forum that (low) heat on the engine during storage actually accelerates moisture buildup inside the engine..comments?

I recently observed something that may be related to your moisture build-up comment. I have a home-made engine dehydrator that I operate with crude controller that runs the system 30 minutes per day, regardless of crank case humidity. I have a couple of in-line humidity sensors that I use to monitor humidity levels.

Immediately following a flight, I see >80% RH. After it runs for a bit, it drops to 50%. Typically, when I return to the hanger for the next flight (nominally a week later), I see 20-30% RH. So far so good.

Now, with the colder weather, I turn on a remote-controlled sump heater 8-10hrs before a planned flight. When I arrive at the hanger, the RH is >90%. Turning on the dehumidifier starts to bring the humidity down. My observation is that heating the oil seems to "release" moisture into the sump. I'm not sure of the mechanism, but I'm surprised at the observation.

 

[BillL]

Condensate from shutdown to dryer flow?

Dean, your observation of humidity increase is key. We do have to be careful to convert %RH and F to dew point and not just to think about %RH.

My dryer timer stuck on and instead of 60 min, stayed on for 25hrs. I unplugged the sensors and left them in place but took the logger home to download and clear. The data recorder showed 1.5% at 40F "ish".

The next day ~24 hrs - I went back and hooked the logger back to the sensors and it read 23% RH at about the same temp. Now -this is rough and maybe not accurate temps, but I left the logger back on to track any additional change in the crankcase. It has not been down loaded. My new logger will record 1/min for ~10 days so will have the storage to do a 3 day run then do a heating cycle.

My dryer has a purge cycle on it that will clear the crankcase with ambient air in 3 min, but runs for 5. It takes 5-8 min after shutdown to get the dryer hooked and operational. The idea is to purge to minimize condensation of the cooling engine gasses. If water gets into the oil, it might take a while to get that out.

Edit - -my humidity and temperature sensors are 4" down in the dipstick tube.

 

[von_flyer]

Preheater effect on dehydration

This is test data from a datalogger with probes in the oil fill tube. I run my dehydrator 100% of the time. It's closed loop so I am not introducing new air into the engine.
Data shows the effect on %RH while preheating/cooling/preheating cycle starting with a cold engine. The preheater is the 120v heating pad on the bottom of the case of the engine.

 

[Tcheairs]

So John, can one conclude from your chart that keeping the engine preheated (in my case with a constant temp of 80* via a ducted 400w ceramic heater to one of the exhaust pipes) and running the Mojave at the same time should result in a constant low % ph?

 

[von_flyer]

My interpretation of the data shows that is the case. However there may be exterior areas of warm/cold transition that may condense with ambient temperature changes. This data is only inside the crankcase below the pistons.

 

[rockwoodrv9]

Now I am a little confused. Am I better to not heat the engine and just run the dehydrator or heat it and run the dehydrator?

My sensor shows 10%-18% most of the time when the heater is on or off. Of course it is more after a flight but comes down within an hour or so.

The weather has been so crappy up here I havent been able to fly for over 2 weeks. That is about the longest I have gone since I got my license!

 

[Tcheairs]

Rockwood, I assume that you have a hygrometer with a probe that you insert into the oil fill tube (or somewhere) to take your % readings. What kind of indicator do you have. And are you able to leave it inserted while using the Mojave (dryer)? If so, how? I can't see from your photos how exactly your system works.

 

[Dean Pichon]

Now I am a little confused. Am I better to not heat the engine and just run the dehydrator or heat it and run the dehydrator?

My sensor shows 10%-18% most of the time when the heater is on or off. Of course it is more after a flight but comes down within an hour or so.

The weather has been so crappy up here I havent been able to fly for over 2 weeks. That is about the longest I have gone since I got my license!

My take on this is that you want to run the dehydrator as necessary to keep the RH low so there is no risk of condensation which, in turn, will reduce the likelihood of corrosion. Heating the oil during cold temperature operations lowers the viscosity which reduces start-up wear.

I need a better controller for my system so as the oil temp rises while the sump heater is on, the dehydrator can react and bring the RH back down. (Recall, I stated in a previous post, my system runs only 30 minutes a day, regardless of humidity or temperature.)

 

[rv8ch]

My take on this is that you want to run the dehydrator as necessary to keep the RH low so there is no risk of condensation which, in turn, will reduce the likelihood of corrosion. Heating the oil during cold temperature operations lowers the viscosity which reduces start-up wear.

I need a better controller for my system so as the oil temp rises while the sump heater is on, the dehydrator can react and bring the RH back down. (Recall, I stated in a previous post, my system runs only 30 minutes a day, regardless of humidity or temperature.)

If your RH is below 40% you should not get rust. Preheat as needed before you fly, but not sure there is any advantage to heating the engine 24x7. I've read in some places that sell engine heaters that they don't recommend running them all the time.

 

[rockwoodrv9]

My system has a sensor that is in the silica beads so it measures the air coming in from the oil dip stick plug. It feeds air from the container to the oil breather tube. I’m sure it isn’t as accurate as something in the engine but it does measure the air right as it comes into the beads. If it gets up to 25% I will heat the beads to renew them then it goes back to 10%. It is the system Jon made for me.

 

[Tcheairs]

So it is necessary to heat and dry the beads in Jon's system? Do you remove them from the closed container and put them in a toaster oven or something?

 

[Tcheairs]

Interesting reading here on this subject. Test results of dehumidifiers and Camguard. Click to download the pdf file.

 

[koupster]

Now I am a little confused. Am I better to not heat the engine and just run the dehydrator or heat it and run the dehydrator?

Rocky,

My take on this is that only heating the sump may condense moisture on the cold upper reaches of the engine ( where the camshaft lives). You've got it covered with the heater ducting into the inlet.

Ducting warm air into an exhaust pipe? That air may meet two closed exhaust valves; warming mostly just the pipes. Better to duct the air into the opening around the pipes while blocking the inlets, or ducting it into an inlet while blocking the other.

 

[Dean Pichon]

If your RH is below 40% you should not get rust. Preheat as needed before you fly, but not sure there is any advantage to heating the engine 24x7. I've read in some places that sell engine heaters that they don't recommend running them all the time.

Agreed. I only run the sump heater in advance of a planned flight.

 

[rockwoodrv9]

So it is necessary to heat and dry the beads in Jon's system? Do you remove them from the closed container and put them in a toaster oven or something?

I heat them about every other month just to keep it as low as I can. It is really moist here in Michigan. The system works great and I am happy with it.

 

[Tcheairs]

Routing the heated air into the exhaust pipes (my experience) results in an entire heated engine (80*-90*) based on readings taken with the infrared thermometer gun. Yes, I do plug the intakes and cover the cowling with a heavy freezer blanket. I would think that heating a (mostly full) oil sump would also transmit heat to the entire engine within a few hours. Easy to check with an infrared thermometer.

Question is does keeping the engine at a relatively even temperature help with inhibiting the moisture accumulation. Check out the article I posted previously on 1-7.

 

[Tcheairs]

The following article posted by Ken Sutton addresses the heart of the discussions contained in this thread including engine preheating, moisture removal and the use of additives (Camguard) in the engine oil. It's a must read for me at least for a better understanding of all of the physics at play in keeping our engines dry.

https://www.reiffpreheat.com/Article-Sutton.pdf

 

[calvind]

The oxygen concentrator re-bedded with silica gel is producing about 3 lpm with <1% RH 10 minutes after startup with a 50F 60% RH input stream. Reading up on adsorbents has me wondering what this media is doing to the composition of the output stream so I have ordered a fuel cell type O2 sensor (Asair AO-02, 0-100% range) to investigate that. If the O2 concentration is being significantly increased then it might be time to try Bill's idea of using CMS220 which should decrease the O2 concentration. Will report back in a few weeks after the sensor arrives from China.

 

[calvind]

Today the A0-02 oxygen sensor came so I used it to measure the oxygen concentration of the dehydrator output stream. It measures slightly higher than the ambient air, about 21.4% versus a presumed 20.9%. So silica gel does not seem to have a significant adverse effect on oxygen concentration. The input stream today was 50F and 76% RH and the output stream settled out at 2% RH.