Regulator Buying Guide: Help Me Choose a Regulator
Precision Regulation When Purity Matters.
The wrong gas regulator can waste gas, contaminate a sample, give an unstable instrument baseline, and in the worst case create a hazard. This guide asks the same questions Harris Products Group asks before it recommends a regulator: what gas and purity, what supply source, what delivery pressure, how much flow, and single- or two-stage. Most people get through it in a few minutes. Have your cylinder (or its label) nearby.
At the end you’ll know:
- which Harris regulator model fits your gas and purity grade,
- which CGA inlet connection you need,
- single-stage or two-stage,
- the right delivery-pressure range, and
- what outlet valve, fittings and accessories to order.
Still unsure? Call 1-888-641-2267 or email sales@labregulator.com. Labregulator.com is a division of Cryo Inc., serving labs since 1978.
Jump to: Express lanes · 1. Gas · 2. Purity · 3. Connection · 4. Single vs. two-stage · 5. Pressure · 6. Flow · 7. Outlet & accessories · 8. Checklist · FAQ
Express Lanes: Special Applications
If one of these describes your job, you can go straight to the right product.
| If you need… | Go to | Why |
|---|---|---|
| A regulator for a CO2 incubator on a single cylinder | CO2 Incubator Regulators | Two-stage CO2 (CGA 320) regulator with a low delivery range and a hose-barb outlet for plastic tubing. Most incubators need only about 10–20 psig at very low flow |
| No downtime on CO2 incubators (two cylinders, automatic changeover) | CO2 Manifold for Incubators | Switches to the reserve cylinder when the primary runs out |
| Gas withdrawal from a liquid cylinder (dewar), or laser assist gas | Special Application Regulators: Harris HP405 | Single-stage, high flow capacity (Cv 0.37), for the fairly constant pressure of a liquid cylinder’s gas-use valve. CGA 320, 540, 580 |
| High delivery pressure (above 500 psig): pressure testing, charging accumulators | Special Application Regulators: Harris HP8700 | Single-stage high-pressure regulator. Harris offers 0–800 up to 0–6000 psig. We stock 0–1500 and 0–2500 psig in CGA 580 |
| Welding shielding gas (MIG/TIG argon, Ar/CO2, CO2) | Contact Us | Welding is set by flow (CFH), so you need a flowmeter or flowgauge regulator, not a lab pressure regulator. Available by request |
Not on the list? Start at Step 1.
Step 1: What Gas Will You Use?
The gas decides almost everything else: the inlet connection, which materials are safe, and the special precautions. In the US, the Compressed Gas Association (CGA) assigns cylinder valve outlet connections by gas family (standard CGA V-1). The fittings are made different on purpose, so a regulator for one gas family can’t easily be connected to an incompatible one.
Quick reference: common gases
| Gas | Typical CGA connection (US, cylinders up to 3000 psig) | Recommended Harris regulator | Notes |
|---|---|---|---|
| Nitrogen, Argon, Helium (also Krypton, Neon, Xenon) | CGA 580 | By purity: GP402 (industrial) · HP702 (to 5.0) · HP722C (5.0 UHP / GC) · HP742 (6.0+) | The most common lab connection. High-pressure cylinders use CGA 680 (~3500 psig) or 677 (~6000 psig), which pair with the HP8700. Ask us |
| Oxygen | CGA 540 | HP702 (high purity) or HP722C (research / UHP) | These are the models Harris recommends for oxygen. Keep everything oil- and grease-free. Open the valve slowly |
| Hydrogen, Methane, Carbon Monoxide, Ethylene | CGA 350 (left-hand thread) | HP702 · HP722C · HP742, by purity | Flammable: add a flashback arrestor and check valve, vent the relief safely, keep away from ignition sources |
| Carbon Dioxide | CGA 320 (flat washer, replace at every cylinder change) | HP702 (general) · HP722C (research) · HP742 (corrosive mixtures) · HP405 (liquid cylinder) | Can freeze up at high flow (see below). Incubators: see Express Lanes |
| Air, USP / medical / breathing | CGA 346 | HP702 · HP722C · HP742 (GP402 also offered) | Medical applications have their own regulatory requirements. Ask us |
| Air, industrial / zero air; SF6 | CGA 590 (left-hand internal thread) | HP702 · HP722C · HP742 (GP402 also offered) | — |
| Corrosives: chlorine, sulfur dioxide, nitric oxide | CGA 660 (washer) | HP742 stainless (HP742 CGA 660) | Brass is not suitable. Use a cross-purge assembly. Inert-purge at every startup and shutdown |
| HCl, H2S, HBr | CGA 330 (washer) | HP742 in CGA 330: available by request | As above |
| Ammonia (anhydrous) | CGA 240 or 705 | HP742 (240/705) or Harris HP701EN electroless-nickel: by request | Brass is not suitable for ammonia |
| Acetylene, Propane, Butane | CGA 510 (some acetylene cylinders: 300) | Harris 510 versions, and the Model 717 for atomic-absorption acetylene: by request | Acetylene must never be delivered above 15 psig. Open an acetylene cylinder valve no more than one turn |
| Nitrous oxide | CGA 326 | Contact us | Oxidizer. Treat like oxygen (oil-free) |
| Calibration / specialty mixtures | Depends on the mixture (see below). Read the cylinder valve | HP722C, or HP742 for 6.0 or reactive components | — |
| Lecture bottles | CGA 170 / 180 | Harris lecture-bottle regulators: by request | — |
Full list: our CGA Charts page. Always confirm against the connection on your actual cylinder. Your gas supplier makes the final call, especially for mixtures.
Gas-specific cautions
Oxygen. Oxygen makes ordinary materials burn violently. Use an HP702 or HP722C in CGA 540, the models Harris recommends for oxygen. Dedicate the regulator to oxygen. Never attach equipment that has oil or grease on it, and never lubricate an oxygen regulator or cylinder connection. Always open the cylinder valve slowly, because fast pressurization heats the gas and can ignite contaminants. The GP402 is sold in CGA 540, but Harris doesn’t list it among its oxygen recommendations, so we steer oxygen users to the HP702 or HP722C.
Hydrogen and flammables. CGA 350 uses a left-hand thread, usually with a notched nut. Keep cylinders away from ignition sources and ventilate the area. Fit a flashback arrestor and check valve where the equipment or code requires it. Pipe relief-valve and purge vents to a safe location. Leak-test with leak-detector solution, never with a flame.
Carbon dioxide. CO2 comes as a liquid in the cylinder, so cylinder pressure stays roughly steady until the liquid is gone, and it rises with temperature. – Below about 60 psig delivery, the expanding gas forms dry-ice “snow” at −70 °F to −100 °F. The dry ice can plug the outlet or hold the regulator seat open, which shows up as pressure creep or erratic pressure. – The worst case is a warm (90 °F or more), full (1100 psi or more) cylinder at high flow. – Frost on the outside of the regulator is only moisture from the air, and Harris says it typically has no effect on performance. – Low-flow uses like incubators rarely have trouble. – For high or continuous CO2 flow, Harris makes the HP705 electrically heated two-stage regulator (200 W, rated for 100 scfh CO2 continuous under worst-case freeze-up conditions), available by request. – Never draw gas through a regulator from a siphon (dip-tube) CO2 cylinder. Those cylinders are for liquid service.
Corrosive and toxic gases. These need the HP742 (316L stainless body, 316L diaphragm, PTFE seat). Brass regulators (GP402, HP702, HP722C) are not for these gases. – Use a cross-purge assembly, and purge with inert gas at every startup and shutdown. – A ventilated gas cabinet and gas detection are often required under your site’s safety program. – Confirm compatibility for your exact gas with us before ordering.
Specialty and calibration mixes. The CGA on a mixture is set by its composition, so read the valve. – Harris’s guidance for oxygen-containing mixes: less than 5% O2 → CGA 580; 5% to under 23.5% O2 → CGA 590; 23.5% O2 or more → CGA 296. – Many medical mixtures use CGA 500. We stock the HP702 in CGA 500. – Calibration standards with low-ppm reactive components (H2S, SO2, NO, HCl) are best on the HP742, which has a stainless wetted path and low internal volume.
➡ Next: know your gas and CGA? Go to Step 2.
Step 2: How Pure Does the Gas Have to Stay?
A regulator can add contamination to your gas through its diaphragm, internal volume and leaks. Harris builds four purity tiers, and the tier should match the grade of gas you buy.
| Gas grade / service | Harris model | Construction | Helium leak rate (inboard) | Shop (store category) |
|---|---|---|---|---|
| Industrial, up to grade 4.0 (99.99%): purging, pressure testing, non-critical inerting | GP402 two-stage | Brass body, neoprene diaphragm | Not specified | Economy Application Regulators |
| High purity, up to grade 5.0 (99.999%): GC carrier and detector gases, blanketing, purging, incubators | HP702 two-stage | Plated brass, 302 stainless diaphragm, PTFE seat | 1×10⁻⁸ cc/s | General Purpose Regulators (the store lists the HP702 here) |
| Grade 5.0 UHP: GC, research gases, process analyzers, EPA protocol, emissions, laser gas | HP722C two-stage | Plated brass barstock, 316L stainless diaphragm, PTFE seat | 1×10⁻⁹ cc/s | High Purity Regulators |
| Grade 6.0 (99.9999%) and higher, corrosive gases, reactive calibration mixtures | HP742 two-stage | 316L stainless barstock body, 316L diaphragm, PTFE seat | 1×10⁻⁹ cc/s | Stainless Steel Regulators |
Key points – The diaphragm matters. Neoprene (GP402) is fine for industrial gas, but Harris doesn’t recommend it for high purity. Every high-purity tier uses a stainless steel diaphragm. – Brass vs. stainless. The brass-barstock HP722C covers grade 5.0 UHP and GC work. Choose the stainless HP742 for grade 6.0+, for corrosive or reactive gases, or for corrosive surroundings. – Match up, not down. Putting 5.0 or 6.0 gas through a lower-tier regulator wastes the money you spent on purity.
Note on naming: our “General Purpose Regulators” category holds the Harris HP702, which Harris classes as a high-purity regulator (up to grade 5.0). Harris’s own “General Purpose” line is the GP402, which we list under “Economy Application Regulators.”
➡ Next: Step 3.
Step 3: Where Does the Regulator Connect?
3A. Cylinder, liquid cylinder, line, or manifold?
| Source | What you need | Where |
|---|---|---|
| High-pressure cylinder (most common) | A cylinder regulator (two-stage for steady delivery) with the CGA inlet that matches the valve | GP402 / HP702 / HP722C / HP742 from Step 2 |
| Liquid cylinder (dewar), gas-use valve | A single-stage regulator, because liquid-cylinder pressure is fairly constant | Harris HP405. ⚠ Never connect a regulator to the liquid-withdrawal valve |
| Already-regulated pipeline, wall outlet or point-of-use drop | A line regulator: single-stage, one delivery gauge. Harris makes GP403, HP703, HP723C and HP743 (matching the four purity tiers), plus PNL point-of-use panels | Available by request: Contact Us |
| Multiple cylinders / no-downtime supply | A switchover / manifold system | CO2 incubators: CO2 Manifold. Other gases: Harris semi-automatic and automatic switchovers by request, Contact Us |
⚠ Never put a line regulator on a cylinder. Line regulators aren’t built for cylinder pressure.
3B. How to find your cylinder’s CGA connection
- Look at the cylinder valve outlet. Many valves have the CGA number stamped on the valve body near the outlet.
- Read the cylinder label (gas name and grade) and compare it with our CGA Charts.
- Check the thread and seal. CGA 350, 510 and 590 are left-hand threads, and their nuts are often notched. CGA 320, 330, 660 and 705 seal with a flat washer, so use a new washer at every cylinder change. Most other CGAs seal metal to metal, so don’t use tape or sealant on the CGA connection.
- For mixtures, or if you’re unsure, ask your gas supplier which CGA they fill your product with.
- Order the regulator with that exact CGA number. Every regulator we list states its CGA connection.
Never use an adapter to fit a regulator to a different CGA family, and never move a regulator out of oxygen or flammable service into another service. If the regulator won’t thread on, you have the wrong CGA. Don’t force it.
➡ Next: Step 4.
Step 4: Single-Stage or Two-Stage?
As a cylinder empties, its pressure falls. – In a single-stage regulator, falling inlet pressure makes the delivery pressure rise (this is called supply-pressure effect), so someone has to readjust it. – A two-stage regulator has a factory-set first stage that feeds the adjustable second stage a near-constant intermediate pressure. Delivery stays steady from a full cylinder to an almost empty one.
How big is the difference? Harris rates supply-pressure effect as the change in delivery pressure for each 100 psig drop in inlet pressure. As a cylinder goes from about 2000 to 200 psig:
| Regulator | Supply-pressure effect (psig per 100 psig) | Approximate delivery change, full → nearly empty |
|---|---|---|
| HP722C / HP742 (two-stage) | 0.05 | about 0.9 psi |
| GP402 / HP702 (two-stage) | 0.04 | under 1 psi |
| Harris single-stage UHP (HP721 / HP741) | 1.8 | about 32 psi |
| Single-stage | Two-stage | |
|---|---|---|
| Delivery pressure as the cylinder empties | Rises. Needs periodic readjustment | Stays nearly constant |
| Best for | Constant inlet pressure (liquid cylinders, pipelines, point-of-use), high delivery pressure, or when someone watches the gauge | GC, analyzers, incubators, unattended or overnight runs, any high-pressure cylinder |
| Cost | Usually lower | Usually somewhat higher |
| Our models | HP405 (liquid cylinders), HP8700 (high pressure) | GP402, HP702, HP722C, HP742, CO2 Incubator Regulator |
Rule of thumb: for a high-pressure cylinder feeding an instrument, or anything left unattended, choose two-stage. Harris notes the normal maximum delivery pressure for two-stage regulators is 500 psi. Above that, the HP8700 single-stage is the tool.
➡ Next: Step 5.
Step 5: What Delivery Pressure Do You Need?
A regulator’s internal spring sets its delivery range. The gauge scale does not. Pick a range where your normal working pressure sits near the middle, not crowded at the bottom or pinned at the top. A regulator ranged far above your setpoint will be touchy and unstable at low settings.
Harris delivery ranges by model (psig)
| Model | 0–15 | 0–50 | 0–125 | 0–250 | 0–350 | 0–500 | Above 500 |
|---|---|---|---|---|---|---|---|
| GP402 | ✔ | ✔ | ✔ | ✔ | |||
| HP702 | ✔ | ✔ | ✔ | ✔ | |||
| HP722C | ✔ | ✔ | ✔ | ✔ | ✔ | ||
| HP742 | ✔ | ✔ | ✔ | ✔ | ✔ | ||
| HP405 | ✔ | ✔ | ✔ | ||||
| HP8700 | 0–800, 0–1500, 0–2500, 0–3000, 0–4500, 0–6000 |
What we stock: our GP402, HP702, HP722C and HP742 listings are the 0–125 psig versions. The HP8700 is stocked in 0–1500 and 0–2500 psig. Every other Harris range above is available on request: Contact Us. On the HP405, tell us which range you need when you order.
Picking a range
| Your normal working pressure | Choose |
|---|---|
| Up to about 10 psig (glove-box purge, low-pressure calibration) | 0–15 |
| About 10–35 psig (e.g., CO2 incubators at 10–20 psig) | 0–50 |
| About 40–100 psig (most GC carrier gas and instruments) | 0–125 (stocked) |
| About 150–200 psig | 0–250 |
| About 250–450 psig | 0–500 (HP722C, HP742) or 0–350 / 0–500 (HP405) |
| Above 500 psig | HP8700 (0–800 up to 0–6000) |
Check your instrument manual for the inlet pressure it requires, and then add a margin for line losses.
➡ Next: Step 6.
Step 6: How Much Flow?
Harris is clear on this: regulators don’t measure or control flow. Use a flowmeter or metering valve for that. Every regulator also shows some droop, meaning its delivery pressure falls as flow rises. Smaller, low-internal-volume UHP regulators droop sooner at high flow.
Harris rates flow capacity with the flow coefficient (Cv). Higher Cv means more flow capacity. Use these to compare models:
| Model | Cv | Relative flow capacity | Typical fit |
|---|---|---|---|
| HP405 | 0.37 | Highest of our regulators | Laser assist gas, purging, liquid-cylinder withdrawal |
| GP402 / HP702 | 0.15 | Medium | Purging, blanketing, general lab, multiple instruments |
| HP8700 | 0.08 | Low (designed for pressure, not flow) | Pressure testing, charging |
| HP722C / HP742 | 0.06 | Lower. Designed for cleanliness and low internal volume | GC, analyzers, calibration standards (mL/min flows) |
- Instrument and GC flows (mL/min): any of these regulators has more than enough capacity.
- High or continuous flow (large purges, process feeds, laser assist): consider the HP702, GP402 or HP405, or ask us about Harris high-flow and dome-loaded regulators. Harris publishes Cv and flow curves rather than a single scfh rating, so tell us your flow and we’ll check it with Harris.
- High-flow CO2: see the HP705 heated regulator in Step 1.
- You need a set flow rate (sccm, LPM, scfh): add a metering valve or flowmeter downstream. Harris specialty-gas flowmeters (SG1000, SG1050, SG1100 series) are available by request.
- Welding shielding gas: MIG and TIG are set by flow, so use a flowmeter or flowgauge regulator. Ask us for options.
➡ Next: Step 7.
Step 7: Outlet Connection & Accessories
7A. Outlet valve and fitting
| Model (as we stock it) | Standard outlet | Relief valve |
|---|---|---|
| GP402 | 1/4″ MNPT needle valve | Internal, self-reseating |
| HP702 | 1/4″ MNPT needle valve | External relief, standard |
| HP722C | 1/4″ MNPT needle valve | External relief, standard |
| HP742 | 1/4″ FNPT diaphragm valve (packless and leak-tight, which suits UHP and corrosive service) | Optional. Ask for it if your system needs one |
| HP405 | 1/4″ stainless tube fitting (or 1/4″ FNPT port) | Internal, self-reseating |
| HP8700 | 1/4″ NPT with stainless 1/4″ tube fitting | — |
| CO2 Incubator Regulator | Hose barb for flexible plastic tubing | — |
Other Harris outlets are available by request, including hose barbs, tube fittings, FNPT ports, MNPT nipples and diaphragm valves. Use compression (tube) fittings with copper or stainless tubing and hose barbs with plastic tubing. Mixing them causes leaks. Thread sealant or PTFE tape goes on NPT threads only, never on CGA cylinder connections or tube fittings.
A regulator’s relief valve protects the regulator. Add your own downstream relief if your equipment is rated below the regulator’s maximum delivery pressure.
7B. Accessories checklist
| Accessory | When you need it | Where |
|---|---|---|
| Cylinder bench clamp or wall bracket | Always. Every cylinder must be secured | Accessories |
| CGA flat washers (320, 330, 660, 705) | Every cylinder change | Contact Us |
| Tee or cross purge assembly | Toxic, corrosive, flammable or high-purity service. Purges air and moisture out at startup and process gas out before you disconnect | By request |
| Flashback arrestor and check valve | Flammable gases, especially where fuel gas meets oxygen or air | By request |
| Downstream relief valve | Equipment rated below the regulator’s maximum delivery pressure | By request |
| Replacement gauges | Damaged gauges, or ones that won’t return to zero. The range must match the regulator | By request |
| HP705 heated CO2 regulator | High or continuous CO2 flow | By request |
| Flowmeters (SG1000 / SG1050 / SG1100) | You need to set or read flow | By request |
| Protocol / mounting stations, switchovers | Wall-mounted regulator stations, or no-downtime supply for gases other than incubator CO2 | By request |
➡ Next: Step 8.
Step 8: Final Checklist
Before you add to cart, confirm:
- ☐ Gas (and the full composition, if it’s a mixture)
- ☐ CGA connection on the cylinder valve (e.g., 580, 540, 350, 320, 590, 346, 660, 500)
- ☐ Purity grade: ≤4.0 → GP402 · ≤5.0 → HP702 · 5.0 UHP/GC → HP722C · 6.0+ or corrosive → HP742
- ☐ Oxygen? HP702 or HP722C, oil-free
- ☐ Single- or two-stage (two-stage for cylinders feeding instruments or unattended use)
- ☐ Delivery range with your setpoint near mid-scale (stocked: 0–125. Others by request)
- ☐ Flow: compare Cv, and add a flowmeter or metering valve if you need a set flow
- ☐ Outlet valve and fitting to match your tubing. Relief valve if needed (optional on the HP742)
- ☐ Accessories: cylinder restraint, washers, purge assembly, flashback arrestor and check valve
Safe installation in brief
- Secure the cylinder.
- Inspect the valve and regulator threads for damage, dirt, oil or grease. This is critical for oxygen.
- Attach the regulator and wrench-tighten. Never force a cross-threaded connection.
- Back the adjusting knob fully out (counter-clockwise).
- Stand with the cylinder between you and the regulator, never in front of the gauges, and open the cylinder valve slowly.
- Set the pressure, then leak-test with leak-detector solution.
- At shutdown, close the cylinder, bleed the regulator, and back out the knob.
About “cracking” a cylinder valve: Harris’s general instructions describe briefly opening (“cracking”) the valve to blow dust out of an inert or non-hazardous industrial-gas cylinder. Never crack the valve on toxic, corrosive, flammable or pyrophoric gases. Use a purge assembly and your site’s procedures instead.
Still not sure? Contact us.
We’ll match the regulator to your application. Have this ready:
- Gas and grade or purity (e.g., 99.999% / 5.0)
- CGA number on the cylinder valve (or a photo of the valve outlet)
- Required delivery pressure (normal and maximum)
- Flow rate (typical and peak)
- Application / instrument (e.g., GC model, incubator, laser, purge)
- Source: cylinder, liquid cylinder or pipeline, and how many cylinders
- Outlet tubing size and material
- Environment: indoor lab, fume hood, outdoors, corrosive atmosphere
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[Button: Shop All Regulators → https://www.labregulator.com/shop/] [Button: Ask a Regulator Expert → https://www.labregulator.com/contact-us/]Frequently Asked Questions
Do I need a single-stage or two-stage regulator?
Choose two-stage when the regulator sits on a high-pressure cylinder and you want steady delivery without readjusting. Harris two-stage regulators change only about 0.04–0.05 psi for every 100 psi the cylinder drops. Single-stage regulators suit constant inlet pressure, such as liquid cylinders, pipelines and point-of-use lines, or very high delivery pressures like the HP8700.
Which Harris regulator should I use for my gas chromatograph?
Match the regulator to your gas grade. The HP702 is rated for gases up to grade 5.0 and is listed by Harris for GC carrier and detector gases. The HP722C is the standard choice for grade 5.0 UHP gas. For grade 6.0 gas or calibration standards with low-ppm reactive components, use the HP742 stainless steel regulator. All three are two-stage.
Do I need a stainless steel regulator for high-purity gas?
Not always. The brass-barstock HP722C, with a 316L stainless diaphragm and PTFE seat, is built for grade 5.0 UHP and GC work. Choose the 316L stainless HP742 for grade 6.0 and higher, for corrosive or reactive gases, or for corrosive surroundings.
Which regulator should I use for oxygen?
Harris recommends the HP702 or HP722C with a CGA 540 inlet for oxygen. Keep the regulator dedicated to oxygen and completely free of oil and grease, and open the cylinder valve slowly. The GP402 is offered in CGA 540, but Harris doesn’t include it in its oxygen recommendations.
How do I find which CGA connection my cylinder uses?
Look for the CGA number stamped on the cylinder valve, check the gas name on the cylinder label, and compare it with our CGA Charts page. Your gas supplier can confirm it, which is especially useful for mixtures. Order the regulator with that exact CGA number. If a regulator won’t thread on, it’s the wrong CGA, so don’t force or adapt it.
Can I use one regulator for several gases?
Only for gases that share the same CGA connection and are compatible with the regulator’s materials. Harris says to use a regulator only with the gases it is intended for. Never move a regulator out of oxygen or flammable service, and never use adapters to cross CGA families.
Why does my CO2 regulator frost or freeze up?
CO2 cools sharply as it expands. Below about 60 psig delivery it forms dry-ice snow at −70 to −100 °F, which can plug the regulator or hold its seat open. Frost on the outside is only moisture from the air. Problems are worst with a warm, full cylinder at high flow. For high or continuous CO2 flow, Harris makes the HP705 electrically heated regulator.
What delivery pressure range should I choose?
Choose a range with your normal working pressure near the middle. 0–15 or 0–50 psig suits low pressures like incubators, 0–125 psig suits most GC and instrument use, 0–250 suits 150–200 psig, and 0–500 is available on the HP722C and HP742. Above 500 psig, use the HP8700. We stock 0–125 psig versions, and other Harris ranges are available on request.
Will a pressure regulator control my flow rate?
No. Regulators control pressure, not flow. Add a metering valve or flowmeter downstream to set a flow. To compare flow capacity, use Harris’s flow coefficient (Cv): HP405 0.37, GP402 and HP702 0.15, HP722C and HP742 0.06. For welding shielding gas, use a flowmeter or flowgauge regulator.
Why doesn’t the delivery pressure drop when I turn the knob down?
Most lab regulators lower their delivery pressure only while gas is flowing. Turning the knob counter-clockwise against a closed, static line won’t change the gauge until downstream gas is released. Open the downstream valve to your instrument or a safe vent and the gauge will settle at the new setting. For toxic or flammable gases, vent only through a purge assembly to a safe exhaust.
Safety Notice
This guide is general information to help you narrow down a choice. It doesn’t replace the Harris instructions supplied with your regulator, your gas supplier’s Safety Data Sheet, or your facility’s safety program and applicable codes (e.g., OSHA, NFPA and CGA publications).
Compressed gases are hazardous. They can be under very high pressure, and they can be flammable, oxidizing, toxic, corrosive or asphyxiating. – Always secure cylinders. – Use only a regulator rated for the specific gas and pressure. – Open cylinder valves slowly. – Leak-test after installation. – Never crack valves on toxic, corrosive or flammable gases. – Have regulators repaired only by Harris or a qualified repair facility.
For corrosive, toxic, flammable or oxygen service, confirm compatibility with us before use. If in doubt, call us at 1-888-641-2267 before you connect anything.