what is a high pressure air compressor?

[Alpo]

How much pressure are we talking?

 

I tried doing a search and I found, listed as high pressure, a 135 PSI. Well that is higher than the normal 125 but I wouldn't really consider it high. And then they were selling a 150 psi. Again that's higher but - high pressure?

 

So how much pressure does a high pressure air compressor make?

[Texas Joker]

Scuba compressors appear to be 4500 psi

[Sgt. C.J. Sabre, SASS #46770]

Mechanics compressors run about 200 I think. Most commercial run about that. Smaller home compressors go anywhere from 50, (paint booth), to about 150. They're like everything else, it depends on how much you want to spend. 

[Jack Spade]

While in the Navy I worked on High pressure air compressors that pumped up the air for the air starters on our gas turbine engines.  I believe they pumped up 1200 psi and they were a two stage compressor.  First stage brought it up to 600 and the second stage 1200.  

[sassnetguy50]

1 hour ago, Texas Joker said:

Scuba compressors appear to be 4500 psi

 PCP air rifle compressors go that high too.  Most rifles max at 2,500-3,500psi.

[watab kid]

the one in my garage is about 120psi to 150 but i do not consider iyt high pressure , its a contractor version , runs pneumatic tools fine 

[Alpo]

20 minutes ago, watab kid said:

the one in my garage is about 120psi to 150 but i do not consider iyt high pressure , its a contractor version , runs pneumatic tools fine 

This is what I've seen. Both home compressors and compressors in the shop - they've all maxed out at 125.

 

I know that scuba tank compressors are much higher, but I don't know how much.

 

And then in the WHAT GUN SHOULD I BUY FOR MY KID TO START WITH thread it is suggested to get an air gun if you have a high pressure compressor.

 

So I wondered how much a high pressure compressor was. If the standard compressor is 125, is high pressure 200? 500? 1,000? How high?

[Subdeacon Joe]

"High pressure" is kind of like "High Capacity," depends on context. A 10 round magazine for a .45 ACP 1911 might be considered to be high capacity. 

 

For home or construction,  pretty much anything over 150psi to 200psi is "high pressure" because just about all pneumatic tools have a maximum operating pressure under 150psi.

 

I imagine some very heavy equipment, and shop tools operate on higher pressures.  And, if course, filling high pressure reserve tanks.

 

[watab kid]

2 hours ago, Alpo said:

This is what I've seen. Both home compressors and compressors in the shop - they've all maxed out at 125.

 

I know that scuba tank compressors are much higher, but I don't know how much.

 

And then in the WHAT GUN SHOULD I BUY FOR MY KID TO START WITH thread it is suggested to get an air gun if you have a high pressure compressor.

 

So I wondered how much a high pressure compressor was. If the standard compressor is 125, is high pressure 200? 500? 1,000? How high?

i have a friend that scuba dives - he has to get his tanks filled at local scuba shop - think that kinda pressure is regulated and inspected regularly , i know the compressed air in the commercial shops that i built were inspected and accredited regularly - i had to provide reports that said what it was to be and how it rated 

[Rooster Ron Wayne]

As a mechanic most of my Adult life .

Any compressor the can run & maintain 150psi .

I would call high pressure. 

Just Sayin. 

Rooster 

[Texas Joker]

Then there are the compressors that creat liquid oxygen for rocket fuel.

 

They use jet turbines to compress air.

[Sgt. C.J. Sabre, SASS #46770]

2 hours ago, Texas Joker said:

Then there are the compressors that creat liquid oxygen for rocket fuel.

Actually most gasses are separated from ambient air by cooling the air to cryogenic temperatures until the individual gasses liquify out of the air, since the various gasses liquify at different temperatures. Once separated, they're pumped into individual storage containers, those huge storage towers you see around the plants.

You are correct though, that when in gas form, they can be compressed back to liquid form, but then the have to be kept in the appropriate cryogenic container.

[Jiminy Cricket]

My compressor is capable of 4500PSI, it has an auto-shutoff feature that allows me to fill my PCP air rifles, more or less, unattended.  The most capacity I have in a PCP is 160cc at 4,350 PSI (300 BAR).  This is a 22 Cal rifle that gets 50 or so shots at full velocity, which is near 1000fps ~

34 ft/lbs.  The 30 Cal gets 20 shots 225cc at 2900PSI.  The 50 Cal rifle gets about 5 full strength shots with 500cc at 3000PSI.

[Texas Lizard]

Hot air....Pelosi

[Chief Rick]

18 hours ago, watab kid said:

i have a friend that scuba dives - he has to get his tanks filled at local scuba shop - think that kinda pressure is regulated and inspected regularly , i know the compressed air in the commercial shops that i built were inspected and accredited regularly - i had to provide reports that said what it was to be and how it rated 

The scuba compressors are not inspected/tested because of the pressure, it's because it's used for breathing air. There are specifications for Class D breathing air. 

 

Grade D breathing air specifications:

Oxygen content: 19.5%–23.5% by volume

Hydrocarbon content: 5 mg/m³ or less (condensed)

Carbon monoxide (CO): 10 ppm or less

Carbon dioxide (CO2): 1,000 ppm or less

Odor: Must be free of any noticeable odor 

[watab kid]

2 hours ago, Chief Rick said:

The scuba compressors are not inspected/tested because of the pressure, it's because it's used for breathing air. There are specifications for Class D breathing air. 

 

Grade D breathing air specifications:

Oxygen content: 19.5%–23.5% by volume

Hydrocarbon content: 5 mg/m³ or less (condensed)

Carbon monoxide (CO): 10 ppm or less

Carbon dioxide (CO2): 1,000 ppm or less

Odor: Must be free of any noticeable odor 

that makes sense , im certain they inspect for clean air but must also inspect pressure to be accurate ?

[Alpo]

I watched them fill a tank at a sporting goods store. The tank was in a tank of water.

 

I assume that was in case they overpressed it and it blew up. The water would absorb the blast. Water would go flying everywhere, but shrapnel wouldn't go flying all through the store cutting customers up.

[El Sobrante Kid]

They put the cylinder in the water to cool it down. Rapidly compressing the air causes heat to build up, and the water helps to mitigate that issue. If a compressed gas cylinder is going to explode, the weak point is the threads where the valve screws into the cylinder. It is rare for a cylinder in good condition to rupture. But, if a cylinder has rust corrosion on the inside, it is possible for the cylinder to rupture in "banana peel" fashion. If the valve rips off it can cause a huge amount of damage. There is an inspection schedule for all compressed gas cylinders, as well as a finite lifetime.

[Barry Sloe]

0-300 psi, low pressure. 

301-600 psi, medium pressure. 

601 & up psi, high pressure. 

That's what I was taught. 

We had both low pressure (100 psi) and high pressure (3000 psi) compressors on the ships I was on.

 

BS

[Chief Rick]

20 hours ago, watab kid said:

that makes sense , im certain they inspect for clean air but must also inspect pressure to be accurate ?

Class D air compressor gauges must be calibrated (I think annually). Not part of the breathing air testing, but yes it is a requirement. 

[Dr. Zook]

On 10/28/2025 at 5:57 PM, Chief Rick said:

The scuba compressors are not inspected/tested because of the pressure, it's because it's used for breathing air. There are specifications for Class D breathing air. 

 

Grade D breathing air specifications:

Oxygen content: 19.5%–23.5% by volume

Hydrocarbon content: 5 mg/m³ or less (condensed)

Carbon monoxide (CO): 10 ppm or less

Carbon dioxide (CO2): 1,000 ppm or less

Odor: Must be free of any noticeable odor 

Chief, can you elaborate on aviators oxygen vs standard regulations?

[watab kid]

4 hours ago, Chief Rick said:

Class D air compressor gauges must be calibrated (I think annually). Not part of the breathing air testing, but yes it is a requirement. 

i expected so , i cant think OSHA doesnt have their fingers in this as its life critical , 

[Sgt. C.J. Sabre, SASS #46770]

1 hour ago, Dr. Zook said:

Chief, can you elaborate on aviators oxygen vs standard regulations?

Industrial O2 is just pumped from the tower. Medical O2 comes from the same source, but is tested for purity to 99.7% pure. Aviators is also pumped from the same source, but tested for moisture. 

[Dr. Zook]

Interesting,  thank you- flew medivac for several years and our med o2 was always on one cart and aviators o2 was a different cart. we could transfill our own bottles but couldnt touch the AV bottles. We did transition from steel bottles to aluminum for the D/E size but the M tanks remained steel.

[Chief Rick]

14 hours ago, Sgt. C.J. Sabre, SASS #46770 said:

Industrial O2 is just pumped from the tower. Medical O2 comes from the same source, but is tested for purity to 99.7% pure. Aviators is also pumped from the same source, but tested for moisture. 

Also, Grade D breathing air is NOT medical or aviation grade oxygen.  Grade D breathing air is just regular air (19.5%-23.5% O2 by volume) under pressure, with the above specifications.

[Sgt. C.J. Sabre, SASS #46770]

19 minutes ago, Chief Rick said:

Also, Grade D breathing air is NOT medical or aviation grade oxygen.  Grade D breathing air is just regular air (19.5%-23.5% O2 by volume) under pressure, with the above specifications.

Correct. Plain old Compressed Air is pumped Nitrogen at about 79% with Oxygen added at about 21%, not just compressed atmospheric air as many presume. Breathing Air IS just compressed atmospheric air. Like Medical Oxygen, Medical Air is the same pumped mixture as Compressed Air, just Certified.

[SHOOTIN FOX]

Dewalt shop air compressor. Diving compressor can go to 3500 psi.

[El Chapo]

On 10/28/2025 at 9:18 PM, watab kid said:

that makes sense , im certain they inspect for clean air but must also inspect pressure to be accurate ?

 

Every scuba diver has a pressure gauge and is going to check that not only before they go below but while they're below to ensure they don't even get close to out of air.  Although the surface is "always available" in recreational diving, nobody ever wants to be out of air, and the training is to do a safety stop at ~15 feet even though it's not technically necessary.  The short version is that nobody needs to double check that pressure as so kind of regulation, as the will to live is enough for me to do it myself.

[watab kid]

1 hour ago, El Chapo said:

 

Every scuba diver has a pressure gauge and is going to check that not only before they go below but while they're below to ensure they don't even get close to out of air.  Although the surface is "always available" in recreational diving, nobody ever wants to be out of air, and the training is to do a safety stop at ~15 feet even though it's not technically necessary.  The short version is that nobody needs to double check that pressure as so kind of regulation, as the will to live is enough for me to do it myself.

OK < i get this but i cant believe OSHA doesnt have their nose under the tent here , i actually have a very good friend that dives , he is also a quad , so ill ask him about this 

[El Chapo]

On 10/30/2025 at 8:43 PM, watab kid said:

OK < i get this but i cant believe OSHA doesnt have their nose under the tent here , i actually have a very good friend that dives , he is also a quad , so ill ask him about this 

OSHA probably does have all kinds of regulations for commercial diving, but the OSH act has nothing to do with recreational diving.

[watab kid]

3 hours ago, El Chapo said:

OSHA probably does have all kinds of regulations for commercial diving, but the OSH act has nothing to do with recreational diving.

interesting , i thought they might stick their nose into everything should they choose to , ill be honest here , my past experience with them was they were all about the fines and very little to do with compliance and informing