How Much Filtration is Too Much Filtration

[divingtactics]

It seems that the more filters you have, the greater release of CO2 there will be from the Molecular Sieve when a compressor is started after a resting period.

How long do you run your compressors with the whip open to allow for this CO2 to escape? The more filtration you have, it seems the longer you may need to run your compressor with the dump or whip open.

Is it essential that filters are kept under pressure when the compressor is not in use and only depressurized when the filter element is being replaced?

Is it important to have a pressure maintaining valve after each aftermarket filter or just the primary one on the Bauer compressor? I would think that there should be another one after the last aftermarket filter to increase the dwell time.

Is is better for the separators and the intercooling tubes to keep the first to 3rd/4th stage under pressure constantly to keep rust and corrosion/oxidization away?

Interested in informed discussion on this.

Jim, Craig, Pesky, Tobin or others - any thoughts?

 

[frogman62]

It seems you have more questions than we have answers.
I'm sorry, but I have never considered CO2 to be an issue and have never had this issue occur in testing air quality in 40 years. I have never opened a fill whip to allow CO2 to "escape" and filled thousands of scuba cylinders over 30 years at the dive shop.
I don't recommend keeping the filter pressurized when not in use - in fact eliminate the pressure backwards through the moisture trap to blow any moist air that gets through the moisture trap to be pushed backwards from the bottom of the filter cartridge. I always want the PMV after the filter and the drain valve to be closed when not in use.

The most important location of the PMV is after the final filter to increase the dwell time. There is no reason to have one before the moisture trap and filter system unless the compressor has a free floating final stage cylinder and the PMV is there to create back pressure to keep the final stage cylinder in contact with the drive piston.

Rust and corrosion form when the system is not purged and run without pressure to cool and eliminate moisture. There are two main causes of compressor malfunctions --
1st is not running the compressor with no load after filling at high pressure to cool the cylinders and drain the high pressure water saturated air.
2nd Is not running the compressor at least once a month to warm it up and keep it lubricated and "putting it away hot"
Corrosion and oxidation occur when you don't use the compressor enough. I have had compressors run over 2000 hours with only oil changes every 75-100 hours, but they were run 10 to 20 hours every week.
Take a shot guys!!!
Jim Shelden

 

[divingtactics]

Okay, thanks Jim. I tested my CO2 levels with the Kitigawa test tubes and the CO2 was at 2300ppm, over double the US standard and nearly 5 times the Australian Standard of 480ppm. I am filling in an enclosed room within my garage, so will plumb some 3 inch pipe to the outside to catch air from outside into the intake of the Oceanus compressor. I discussed this test with a local supplier and he told me that the filters need to be bled prior to closing the whip and filling and I just wanted some other opinions from the community. While CO2 levels may not be an issue at 100 feet, I am doing dives to over 300 feet and concentrations of anything above recommended levels at those depths do concern me somewhat.

The PZERO filter/separator has a PMV on it set to 150 BAR, so do you think it will be okay to add a second one after my extra filter?

So you are saying that one should run the compressor for how many minutes under no load to allow cooling of the heads?

The corrosion I found was because the compressor had been left sit idle for a few months before I bought it, I have since cleaned the intercooling tubes, Heads, barrels and everything else that I could pull off it and get in the 5 litre ultrasonic cleaner.

I have solenoid controlled timer auto dumps on the unit set to dump for 10 seconds every 10 minutes.

 

[IyaDiver]

DT,

In a big filter tower like say the 27" ones. C02 will drop to as low as 70 PPM when filter is new. This will happen for first few hours. ( So if any dive center posted CO2 lab test level so low, we know they use new filter cartridge for the test and not end of life condition of filter cartridge ).

In a big filter system with proper PMV and proper check valve and filling manifold with line valve, the tower pressure stays good at 2,200 PSI or whatever PMV setting you want. Rarely it will go above 750 PPM C02 after the first few hours of filter life given you those low <250PPM C02 level. Once filter cartridge is into its 20%+ life, the CO2 level will drop and will be like 75 to 100PPM above ambient only , once you reached 50% or more filter life, C02 gets more close to ambient C02 level.

480PPM or 500 PM CO2 air standard is not realistic due to MS nature of C02 adsorbtion and release as pressure swing, however 1000 PPM C02 wont kill you or even generate headache at 50 meters or 6 ATM. Anyone with a nitrox membrane system who has C02 sensor will tell you how much more CO2 they are getting due to the way membrane works. Concentrate the 02 and the C02 also get concentrated. However you are diving to 10 ATM yah.........hhmm 300 feet ...dang that is so deep? Must ask Swampdiver what he thinks, he knows a great deal on the safety point of C02 at such high partial pressure, he is a doctor.
PM him, he will help you for sure.

Your 2300 PPM in a garage is a normal state of CO2 in a confined space but surely I wont want to use that as source air.
If I were you, I would not worry of C02 level when using bigger filter tower but if you need proper air certification, yes C02 level is a pain in the ass if 480PPM is the limit.

I suggest you buy a simple C02 meter from AZ Intruments, it is not bad, 50 PPM accuracy. Their Hong Kong dealer can sell you for under US$200 and you can measure in real time with the help of a dive regulator and those BCD type clip which is an airflow limiter/regulator allowing 2 liters per minute. I can teach you how to taped off the body of the AZ C02 detector to get the air properly channeled to the IR sensor if you are using the wall mounted one.
7721 CO2/Temp. Meter - Wallmount - AZ Instrument Corp.
7752 CO2/Temp. Meter - Handheld - AZ Instrument Corp.

Now, if I were you and wanting low C02 level for sake of safety at 300 feet, without using C02 scrubber, you can actually take advantage of the MS behaviour towards C02.

In your other post :
http://www.scubaboard.com/forums/co...systems/403402-filter-stack-plans-design.html

I reccomended LF65247 filter size, single tower. With your Oceanus 140 liters per minute, I bet you will get at least under 250PPM CO for first 3 hours of filter life or for first 25 M3 of processed air.

Here is an all molecular sieve cartridge and LF65247 ( MS + AC + HP ) , so two big cartridges connected in series, its final C02 level being pumped with 400 liters per minute compressor for first approx 3 hours filter life from new. See C02 v1 to v4
If 3 hours at 400 liters per minute, its like 48 M3 of processed air. No higher than 163 PPM of C02.

NOTE : This filter system is not bled off to reduce C02 level, nor a 2-3 minutes purging with compressor running. Filter tower stay at minimum 2,200 PSI at all times during compressor shut down. Total purging is only done at water separator no 1 and 2 to reduce load during start up and allowing compressor oil to go around well into tight small areas. With 30C ambient and oil temperature never exceeding 40C even at 8 hours non stop run, under a minute warm up and oil circulation is enough at start up.
.

 

[IyaDiver]

Now here is what happened to the same twin huge cartridge filter system after approx 70% of filter life.
See C02 level at 399 PPM. Assuming 50 PPM error, it is still 450PPM.

Note, the dewpoint value in the dewpoint sensor reads -19.4C at 2,800 psi. This is the same as 64.7C at 1 ATM without Greenspan correction factor. With greenspan it is approx 58.7C at 1 ATM.

New filter cartridges can go as low as -73C dewpoint Greenspan corrected or -80C without Greenspan correction, all at 1 ATM.
Filter cartridges will be replaced when at -48C Greenspan corrected, since there is no ice diving involved.
So I am roughly saying 70% plus filter life used up, based on the filter cartridge was at 59C dewpoint Greenspan corrected during the C02 level measurement.

This AZ C02 meter reading is approx +30 PPM at all times. I have a 400 PPM C02 cal-gas, so its verified.

I hope this information will help you to decide what extra filter system you want.
Not many people know MS13x are actually use for C02 scrubbing if one can play with varying pressure.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19970027854_1997049592.pdf\

Dive safe to 300 feet my man........dang I am scared beyond 165 feet.:depressed:


PS
However, I must warn you to calibrate that AZ C02 meter with fresh ambient air often.
When I keep pumping such dry air into the sensor, after approx 20+ hours of use , sensor read CO2 level rise to almost double actual ambient C0, but rise as a fault not actual rise. Calibrate the CO2 unit and all OK. I guess some electronics inside the AZ goes too dry and at under 0.1% humidity and goes banana. You don't need a cal-gas for C02 actually. Ambient fresh C02 level highest is probably 450 PPM in worse case scenario ( open air near the beach ). Whatever reading you get, you add 100PPM, you are safe, if you want to be conservative.

In fact the built-in RH meter in the AZ is now defective, reading at 99% RH always....., again it was too dried out for the last 300+ compressor running. The air temperature you see is the air temperature of the compressor production air after the output twin tower. However I always read it with additional +2 to +3 Celcius because the use of a dive regulator to lower the pressure of the air will do some cooling effect. It actually matches the skin temperature of the water separator no 2, but skin temp is not internal temp. This system uses 3 water separators. The 3rd one is just a defence for the long hose run being used but not bad, get a bit of water out of it.



Later
IYA

 

[divingtactics]

Wow, IYA, a lot of information there and a lot to digest. Hence it has taken me a few days to respond. I see you are suggesting to keep the final filter under pressure (posted by IYA "Filter tower stay at minimum 2,200 PSI at all times during compressor shut down") and Jim is suggesting not to (posted by Frogman62 "I don't recommend keeping the filter pressurized when not in use - in fact eliminate the pressure backwards through the moisture trap to blow any moist air that gets through the moisture trap to be pushed backwards from the bottom of the filter cartridge".) Not sure who is right here, Gabe, maybe you can offer some advice on this. IYA, you certainly seem to know your stuff and have the test data to support it, so I'm leaning towards keeping it pressurized during non use and just purging the 1st to 2nd separator at the conclusion of filling, but like Jim suggests, I do like to blow the last bit of water vapor out of the system when the compressor is off. I'm a little confused as what is the best practice here now because I know Jim Sheldon has been building compressors for years too.

I don't need an air test cert as it is just my own personal filling station and I just bought the Kitigawa system to see how it was performing. It has a variable flow regulator, which will allow me to send 2Lpm through to a CO2 tester if I buy one. It seems that high CO2 levels are quite typical in small home systems that are fed from inside rooms. I will be adding a large 3-inch pipe to the compressor intake and plumbing it to an outside air source and adding most likely a 33-inch tower like you suggested, so I should be able to get the levels down quite a bit by just doing that. The Tube system for measuring is also apparently not very accurate, so I may have to look at what you suggest with electronic test equipment.

Dew Point seems to be a very important factor in filtration working correctly but I know very little about it short of your posts above. My room temperatures are from 18 C in the winter to around 25 C in the summer. If I start the compressor and run it for an hour, the inside temperature of the room will rise about 4 to 6 degrees, so I may need to also look into adding a fan or air conditioning duct into the room to keep the humidity and temperature down. I also think that my filtration should be better and temperatures lower when I route the intake air from outside the room too.

This has been a great opportunity for me to learn a lot more about filtration and I thank you for the time you have taken and the level of detail that you have gone into for me.

Kind regards,

Jason

 

[IyaDiver]

Hi Jason,

I like keeping my P41 and P2 ( P61 ) towers pressurized because they all have stand alone water separator.

The P21 and P31 is a combo water separator and filter housing. In a combo like P21 the outer diameter is water separator section and wet at all time, the inner diameter is the actual filter cartridge holder. So in theory your filter cartrigde is sharing a same air space with lots of water and juicing out that water is a good thing for a P21 and P31.

If you mod your P21 as as water separator only, you have PMV on its right side and there will be another check valve after PMV before the huge additional filter tower. So your water separator which is the P21 is no more sharing its wet air space with the new bigger filter tower. So there is no point for me in bleeding my P41 or say a P2/P61 tower because of the separate chambers between filter tower and the water separator and there is a check valve. Check valve is really good at keeping the tower pressurized. There is no water at all in the filter tower. What water vapor there is, all adsorbed by the MS 13X and not physical liquid water.


Now the CO2 thingy. If C02 release from MS13X is because of pressure change, pressure going down I mean. PMV will release air from a filter tower only when above its set pressure........say mine at 2,200 psi. So when a filter tower is left at 2,200psi and scuba tank is still 0 to 2,200 psi, the filter tower does not experience any significant pressure change as long as compressor is running. The pressure change only occur after the PMV. The tower itself will hold 2,200 psi and bleed out the excess. The MS 13X is in the filter tower, it is not within the PMV output section. We must not forget a filter tower is one chamber, anything after the PMV is another "chamber".

When scuba tank have reached 2,200 psi there is a pressure build up by stage 3 ( say a 3 stage compressor ) pushing pressure higher and higher between filter tower to tank. Again there is no pressure drop, in fact pressure increase at filter tower and at scuba tank.

The only time the filter tower and hence the MS 13X experience drastic pressure change is when during a shut down the filter tower is held at 3,000 psi. Then you connect the filter tower to an empty scuba tank and start filling. There will be a sudden pressure decrease in that filter tower from 3,000 psi to 2,200 psi, won't go lower if the PMV is healthy.

All the test I seen of C02 adsorbtion and desorb using pressure swing for MS 13X is limited to 600 psi or so.
I wish I can find one based on our dive compressor pressure swing.

Anyhow, I too been trying to bleed out a P2/P61 tower hoping to flush more C02 but I did not get any crazy increase above 1,000 PPM. At least I can tell you this based on a CO2 meter being used and not by hear say. If you see the research on C02 adsorb/desorb on MS 13X, time is also required, its not an immediate release. Me dont know much too about actual MS 13X C02 behaviour, but my C02 meters been telling me things, as such the fear of C02 now is gone for me. As soon as water vapor is sticking to the MS 13X, C02 values is more stable too. MS 13X will prefer H20 over C02.

Electronic dewpoint sensor like the one I showned is a bitch to install. I would reccomend that humidity sensor paper disc. That electronic sensor is so sensitive, it takes at least 4 hours compressor running to stabilize or reach real dryness value and it is located on the high pressure side and not using a regulator to reduce pressure. Once you go the regulator route, for decreased pressure or for say constant 2 ATM dewpoint reading, sensor reading/stabilization will be even slower. All the o-rings, HP seat and whatever non metal parts of the regulator has water moisture in them. I gave up reading dewpoint at 2 ATM. Only at 163 - 207 BAR the speed of the reading/stabilization works well.

I think 50 to 100 liters per minute is the air flow it is getting. Can't use copper tube, too wet. Forget rubber hose. Minimum is teflon tube or stainless steel being best. After initial installation and 4 hours wait to read, the next day air fill reading will need at least 2 hours compressor running for real good result to read the last 5 to 10% real accurate dewpoint. Say 1 hour run reads -40, the next 1 hour run will give you -43C. If you can run the compressor for 6 hours non stop, that is the best reading at the last hour.
Its sensitivity is really good when it is runned long time. You read at 2,200 psi and later within minutes as 10 of 80CF tanks are climbing to 3,000 psi, the reading will change since it is based on pressure.

Read post #10 & up
http://www.scubaboard.com/forums/co...nding-systems/402644-filter-water-issues.html

http://www.scubaboard.com/forums/co...moisture-disc-electronic-dew-point-meter.html


Do not test air dryness from a tank output, use compressor output.
Tank output is wetter than compressor output. Don't think water vapor don't stick on tank walls.


Don't bother about lowering air humidity for compressor intake. Since the air is compressed, what you get is a 100% humidty in the compression chamber. The best is cooling the compressor with forced air cooling.
Your Oceanus is a 2,200 RPM machine and that is a HOT one.
Start at post 139. It will give you an idea how hot your compressor can be and how bad the heat transfer from a typical cylinder heads at 30C ambient and at the speed your pulley fan is pumping air over the cylinder heads.
The Deco Stop



The air quality measuring instruments I shown you is mine but the air fill center who uses it belongs to a friend in Bali. One day he came to me and wanted to ask for advice on how to have a proper air fill center and he has two of Bauer/Poseidon 200.

So I made him the wish list for the filtration hardware. In my city ( Jakarta ), my air fill center is low hours. Average only 6 tanks a day and its not filling at one go. I am using a Mariner 200 with P41 filter system. I got all these air sensing toys to learn more of air purification for the sake of learning because its fun and rewarding once you have air so clean, you will find a P21 or any filter that small , its air quality is great but not that great. Simply there is not enough dwell time from a small P21 at 200 liters per minute air flow.

Since Bali air-fill center can do a 100 tanks a day in high diving season, where else can I have the chance to run two of a Mariner 200 10 hours a day non-stop and do easy 2500+ tanks a month if not in Bali. So its a win-win solution for me and my friend. I get a laboratory to play with and he gets the best diving air production in the country, not only in Bali. I then decided not install all those air quality sensing toys in Jakarta, but move some to Bali. I have two of each instruments, thinking if all goes well, I will install same toys in Jakarta. Now I decided not to install the electronic dewpoint sensor for Jakarta as the compressor will never run 3 hours non stop every day.....never. I am going for the humidity paper sensor instead for Jakarta use.

I just bought the Drager oil impactor tube. If you are ever buying a Kitigawa oil test tube to detect oil traces in the compressor air production .......DONT. It will not detect oil trace from synthetic one, just like the Drager common oil test tube, it can't detect too. I have not got the chance to test the Drager oil impactor tube though and an expert friend said it won't give REAL honest result as it is limited to 5 liters or so per minute air flow during the test, must test at compressor 100% air flow. That make sense.
http://www.factair.co.uk/_webedit/uploaded-files/All Files/Safe Air Testers/draeger-oil-impactor.pdf

Have fun reading.....

IYA

 

[IyaDiver]

Sorry, I forgot
This is the dewpoint sensor installation, red circle

 

[divingtactics]

Thanks Iya, more great information. Good to see that you do these tests to support what you know and are continuing to learn about these things. Your knowledge is way ahead of mine and I thank you again for your advice and such comprehensive suggestions.

Thanks for the info about the electronic dewpoint sensor, seems like it is best for me to fit the 20/40/60 paper one then.

I am going to do as you and Iain Middlebrook suggest and add the following:

* P21 output
* Check valve (to keep pressure in tower when P21 is bled)
* 33-inch tower (for main filtration - filled with 13X MS and AC)
* Bleed valve (for bleeding when I change the tower filter)
* Moisture visual indicator 20/40/60 (to indicate earlier change of filter as required - I thought it better here to keep ensure the Hopcalite is always dry)
* Hopcalite in Undersea filter housing (to remove ambient CO)
* PMV set to 150 bar (to increase dwell time in tower)
* Check valve (currently there already to stop Oxygen travelling to filters when PP filling through manifold)

I think I will keep the filtration media in the P21 and just change it every 7 hours - it can't hurt. The tower won't need changing as often and I will change the Hopcalite in the little filter every year or so.

So, all up, I will have three separate filtration systems, two with 13xMS and AC and one with just Hopcalite. There will be a check valve between the tower and the Hopcalite filter and a PMV set to 150 bar before the final check valve into the filling manifold. This way, I should be able to bleed my panel down to 0 bar and keep the filters at 150 bar.

As far as the Kitigawa tests go, I knew they wouldn't be too accurate. I did buy the oil mist tubes without knowing about synthetic - never mind. Not sure which way I will go to test oil mist in future but I'd prefer all tests to come out of the compressor output and not via a tank and I can do this if I open the needle valve on my panel bleed a little with the test regulator connected to the whip.

You will have to let me know which centre in Bali has good quality air, so I can go there next time I've over there.

Yep, the Oceanus is a hot little machine alright. I have measured the temperature of my three heads on a very hot day with long filling times with some refrigeration probes, which are ok. They were quite hot, 1st around 85C, second around 105C and third around 96C, so some cooling may help that along with bringing intake air from outside, which will be done later today.

I did the tests that Gabe suggested on the 13x MC, and did three tests:

1. Tested old used 13x MC from the P21 repack - result was that it generated no heat and I could hold it in my hand indefinitely.
2. Tested old used 13x MC from Undersea inline filter original - result was that it generated no heat and I could hold it in my hand indefinitely.
3. Tested new unused 13x MC that I have had for 2 years stored in a plastic container - result was that as soon as I poured it into my hand, I could feel it warming - then as soon as I tipped the first water droplet on to it, I had to throw it on the ground as the heat was intense and instant. So from this test, I can see that the 2 year old stuff is still okay by the look of it - although some seem to suggest that it is no good after a few months. I'd be interested to learn any other testing methods for 13x MC.

Thanks,

Jason

 

[IyaDiver]

Hi Jason,

Glad I can help.

1 pound of MS13X can generate 1,800 btu of heat when adsorbing water said the manufacturer.
Advanced Specialty Gas Equipment Molecular Sieves - Type 13X Molecular Sieve

This is typical, I seen all spec sheet mentioned the same 1,800 btu
1 Btu is supposed to be energy equivalent of heating 1 pound of water to 1 Farenheit, so they said
In simple term, 1800 btu if all released will burn a P21 blue plastic filter cartridge and whatever oil traces which it will SURELY have.
68 gram MS 13X is what you got in a typical non-hopcalite type P21 filter cartridge and there are documented P21 filter housing melt down on this board due to auto condensate failing to dump water and water enter the P21 filter cartridge in decent volume. Ian call this plasma fire, of some sort. To me is simple if 1 pound which is 454 gram = 1800 btu heat release , take average 68 gram which is 6.6 times less or let say only 272 btu heat release ( I think calculation is not this simple....heheehh). 40C is the typical air temperature of air and its oil mist in a P21 at 25C ambient.

Your compressor oil even a synthetic one is a typical 320C auto-ignition temperature ( AIT ) at 1 ATM and it is so if it a Bauer one.
At 200 BAR or 200 ATM, the AIT will be probably under 200C guesstimate if you looked at my gathered data posted at DecoStop.
So aside from CO2 generation from a hot running compressor, the so called filter housing meltdown is quite real, under the right circumstances of new fresh MS 13X and failure of auto-condensate drain.

I done a test recently on an older Mariner 200 with the 50 BAR oil pump. This is the ringless type floating piston used on 3rd stage.
The owner of the compressor is a friend of mine working in a government , they do marine research, sort of. I dont want to do compresor troubleshooting commercially, for friends or my own unit .....OK, I will do.

She ( yes a lady ) said her air production is very smelly.
So I took a look at the compressor and done a few inspection.
1st problem was, the 1.6 liter oil capacity of this block, took in 2 liters of oil.
So too much oil in compressor. So much oil have made it to the entire system.
I told her to send all her tanks for closer inspection as the oil will have made it to the tank. Its true, the tank internal are oil coated.

Second problem was the operator ( her staff ) did not change the filter cartridge intime, I bet 30+ hours of use or more. If I can attached the "smell" of the fiter cartridge in an email.......you will faint hehehehe. Smell like dead rat.

Anyhow back to the compressor. I dont want to clean all aftercooler pipes or the valves. I change new oil and runned it for few hours until water condensate is clear and the P21 receive decent oil in air production. All good.

Now the fun part. I know a compressor using a Honda ( this one is ) is a pain in the ass for CO avoidance at the intake unless you have wind going one direction to blow your CO away and where you place your compressor walls or building at least 20+ meters, better 100% open air on all 4 sides but with sunshade. And if there is no wind, even in a 100% open air area ........you are still getting CO hit into the snorkle.

I am getting 11 PPM CO during test at the lowest of reading from this compressor air production because my place is a building and even at outside garage the compressor is not really in a 100% open air situation and no wind too.
See the attachement, layout where I place the compressor.

Out of curiousity, and I know this compressor will have lots of oil trace on the compression chambers and all air delivery pipes and I also know that at 29C ambient a Mariner 200 runs hot. Too bad my infra red thermo gun is out of action.
So I want to know what composition of X amount of CO is actually produced by the compressor itself ?...aside from suction of the ambient CO from the Honda engine.

So I use a clean air supply with ZERO CO content and feed the compressor from a scuba tank. I open the tank valve just enough for surplus air to occur at the compressor air intake, making sure ambient CO will not be sucked into the compressor since there is positive pressure at the intake provided by the scuba tank. I use the ToxiRAE CO detector no1 to measure ambient CO at compressor intake, making sure I get zero CO and Honda CO production does not get sucked in. See attachment.

I then used ToxiRAE no 2 for final air production CO testing.
I get 3 PPM C0 on the air production with a 100% zero CO air input. This P21 filter cartridge is not using Hopcalite.
This compressor is only runned like a total 30 minutes but I know at 29C anything after 10 minutes and above 150 BAR, 2nd and 3rd stage will be hitting easy 130C plus.

So where do I get the CO from ? Its the oil traces within the compression chamber which is mildly burning, no other source.
The same test with my newer 5 BAR oil pressure Mariner 200 while being forced cooling with a 81,000 liters per minute blower, do not get any CO and I test at the final water separator output before the P41 filter cartridge.

So a mild over heating compressor will produce CO ? Sure. How much ? I dont know if one run the compressor for hours and hours.
Do you know your compressor is getting mild overheating ? Now way unless you install the automatic overheating shutdown which will trigger auto-off at 132-135C ( if a Bauer ) or you install thermo probes like I do or you have a CO detector at output like Fire Station and will auto-off the compressor when certain programmed level of CO is detected at production air side.

Will continue...........