Scuba Diving Regulators: Exploring the Basics of Parts, Types & How it Works

by Joost Nusselder | Last Updated:  08.02.2023
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Thank god you can breathe underwater when you dive, but how in the WORLD does that work?

A diving regulator reduces pressurized air or blended breathing gas to ambient pressure, delivering it to the diver. The gas may be supplied from a cylinder worn by the diver (scuba set) or via a hose from a compressor or a bank of cylinders on the surface (Snuba).

It’s important for you to understand how one of these works so you’ll know what to expect when submerging. Let’s look at that.

What is a diving regulator

Understanding the Lifeline of a Scuba Diver: The Regulator

What is a Scuba Diving Regulator?

Have you ever wondered what it takes to be a scuba diver? Well, it’s not just a snorkel and some flippers! The most important piece of equipment a diver needs is a scuba regulator. It’s the lifeline between you and your air source while diving, and it’s what makes breathing underwater possible.

So, what exactly is a scuba regulator? Here’s the lowdown:

  • It’s a device that connects to your gas cylinder (or tank) and allows you to breathe air from the tank.
  • Together, the regulator and tank make up a self-contained underwater breathing apparatus (SCUBA).
  • It helps ensure your safety and the proper use of your scuba diving equipment.

How Does a Scuba Regulator Work?

It’s time to get technical! Here’s a quick explanation of how a scuba regulator works:

  • It takes the air from your tank and reduces the pressure so you can breathe it.
  • It also has a valve that allows you to control the flow of air from the tank.
  • It also has a mouthpiece that you put in your mouth so you can breathe the air.

So, there you have it! Now you know the basics of how a scuba regulator works. Time to hit the water and explore the depths!

What is a Demand Valve?

What is it?

A demand valve is a device that detects when a diver starts to inhale and supplies them with a breath of air at the same pressure as the surrounding water. It has a chamber that usually contains air at the same pressure as the water, and it’s connected to a mouthpiece, a full-face mask, or a diving helmet.

How Does it Work?

The demand valve has a flexible diaphragm that senses the pressure difference between the air in the chamber and the water outside. This pressure difference is what triggers the valve to open and supply the diver with air. Here’s how it works:

  • When the diver starts to inhale, the air in the chamber is removed and the external water pressure moves the diaphragm inwards, operating a lever that lifts the valve off its seat and releases air into the chamber.
  • The air pressure is then reduced to the same pressure as the surrounding water, supplying the diver with air to breathe.
  • When the diver stops inhaling, the chamber fills until the external pressure is balanced and the diaphragm returns to its rest position, closing the valve.
  • When the diver exhales, one-way valves made from a flexible air-tight material flex outwards, letting the air escape from the chamber.

Where is it Used?

Demand valves are mainly used in open circuit breathing apparatus, where the exhaled air is discharged into the environment and lost. They can also be used in surface supply diving with free-flow masks and helmets, where the air is regulated at the gas panel on the surface. In some cases, the used air can be reclaimed and reused after removing the carbon dioxide and making up the oxygen.

Diving Through the Ages: A Brief History of Underwater Breathing Apparatus

Early Inventions

It’s been a long and winding road to get to the modern-day scuba set. Here’s a brief overview of the key milestones in the history of underwater breathing apparatus:

  • The first recorded demand valve was invented in 1838 in France, but it was soon forgotten.
  • In 1860, Benoît Rouquayrol invented a demand valve with an iron air reservoir to let miners breathe in flooded mines.
  • In 1864, Rouquayrol and French Imperial Navy officer Auguste Denayrouze adapted the regulator for diving.
  • In 1926, Maurice Fernez and Yves Le Prieur patented a hand-controlled constant flow regulator.
  • In 1937 and 1942, Georges Commeinhes from Alsace patented a diving demand valve supplied with air from two gas cylinders.

The Cousteau-Gagnan Apparatus

It wasn’t until December 1942 that the demand valve was developed to the form which gained widespread acceptance. This came about when French naval officer Jacques-Yves Cousteau and engineer Émile Gagnan met in Paris. Gagnan had miniaturized and adapted a Rouquayrol-Denayrouze regulator used for gas generators, and Cousteau suggested it be adapted for diving.

The Single Hose Regulator

In the early 1950s, Australian Ted Eldred invented the single hose regulator, with a mouth held demand valve supplied with low pressure gas from the cylinder valve mounted first stage. This was in response to patent restrictions and stock shortages of the Cousteau-Gagnan apparatus in Australia.

In 1951, E. R. Cross invented the “Sport Diver,” one of the first American-made single-hose regulators. Other early single-hose regulators developed during the 1950s include Rose Aviation’s “Little Rose Pro,” the “Nemrod Snark” (from Spain), and the Sportsways “Waterlung,” designed by diving pioneer Sam LeCocq in 1958.

The single hose regulator was later adapted for surface supplied diving in lightweight helmets and full-face masks in the traditional diving dress.

And the rest, as they say, is history!

What’s the Deal with Scuba Regulators?

The Basics

Scuba diving is all about being able to hang out in the water for extended periods of time, and that means you need a lot of air to breathe. But just carrying around a bunch of air in its basic form won’t get you very far.

The only way to really make a deep dive is to compress and pressurize air into cylinder tanks. That’s where scuba regulators come in. They take the high-pressure air from the tanks and reduce it to a much more manageable level so you can breathe it in through the connected mouthpiece.

The Fun Stuff

So you wanna know how scuba regulators work? Well, it’s actually pretty simple. Think of it like this:

  • The air in the tanks is like a really angry dragon. It’s all locked up and ready to breathe fire.
  • The regulator is like a brave knight. It takes the dragon’s fire and turns it into something much more manageable.
  • And then you, the diver, are like the princess. You get to breathe in the knight’s air and live happily ever after.

See? Scuba regulators are actually pretty cool!

Understanding the Parts of a Scuba Diving Regulator

First Stage Regulator

When you’re ready to dive, you’ll need to get your air tank ready. The air inside is stored under a ton of pressure – about 3,000 pounds per square inch (psi) – so the first stage regulator steps in to reduce that pressure to something more manageable. It attaches to the tank valve and lowers the pressure to an intermediate pressure (about 140psi) and sends it off to the second stage regulator.

Second Stage Regulator

This is the part that goes into your mouth. It takes the intermediate pressure from the first stage and reduces it to the surrounding water pressure, making it easy to breathe. It has a piston or diaphragm construction that starts and stops the airflow.

The mouthpiece, exhaust valve, and emergency purge valve (or button) are all part of the second stage. The exhaust valve lets the air escape when you exhale, and the purge button forces air into the second stage chamber, pushing any water out of the mouthpiece.

The Benefits of a Scuba Diving Regulator

A scuba diving regulator is a lifesaver – literally! Here are some of the benefits:

  • Reduces the pressure from the air tank to a comfortable level
  • Compensates for the decreased pressure in the tank as the air is used and as the diver changes depth
  • Allows you to vomit while still keeping the regulator in your mouth
  • Makes it possible to survive underwater until you can safely return to the surface

The Five Parts of a Scuba Diving Regulator Explained

1. First Stage

The first stage of a scuba diving regulator is like a bridge between the tank and the diver. It reduces the high pressure air in the tank to an intermediate pressure, which is then sent through the low pressure (LP) regulator hoses. This intermediate pressure is still too high to be breathed directly, so it needs to be further reduced.

2. Primary Second Stage

The part of the regulator that a diver puts in their mouth is the second stage. It’s attached to the first stage by a low-pressure hose and it reduces the intermediate pressure air from the regulator hose to an ambient pressure that a diver can breathe. This is the part that a diver normally breathes from during a dive.

3. Alternate Second Stage

The alternate second stage (also known as an alternate air source, buddy regulator, or octopus) is a back-up that is usually not used. It does the same thing as the primary second stage, reducing the intermediate pressure air from the regulator hose to an ambient pressure that a diver can breathe. It’s usually bright colors, like neon yellow, so it can be quickly located in an emergency.

4. Submersible Pressure Gauge and Gauge Console

The submersible pressure gauge (SPG) allows a diver to monitor the amount of air in their scuba tank. It’s connected to the regulator first stage by a high-pressure hose (HP hose) that feeds high-pressure air from the tank directly to the pressure gauge. The console containing the pressure gauge also holds other gauges, like a depth gauge, compass, or dive computer.

5. Low-Pressure Inflator Hose

This low-pressure hose carries intermediate-pressure air from the regulator first stage to the Buoyancy Compensator’s (BC) inflator. This allows divers to add air to the BC from the tank at the touch of a button.

What is a Scuba Diving Regulator First Stage?

The Basics

A scuba diving regulator first stage is the part of the regulator that reduces the high-pressure air from the tank to an intermediate pressure. It’s usually connected to four hoses – three for the second stages and the BC inflator, and one for the pressure gauge.


Here’s a breakdown of the parts that make up a regulator first stage:

  • First Stage Body: This metal cylinder contains the mechanisms that reduce the high-pressure air. It takes the air in one side and then releases it through the low-pressure hoses.
  • Yoke: This is the metal oval that fits over the tank valve and holds the regulator in place. It’s equipped with a yoke screw that tightens the regulator to the tank.
  • Dust Cap: This rubber cap seals the opening on the first stage, so no water can enter.
  • Port/Port Plug: Regulator first stages have multiple openings, or ports, for hoses to be screwed into. They also have plugs to close the ports when they’re not in use.

In Summary

So there you have it – the regulator first stage is the part of the regulator that reduces the high-pressure air from the tank to an intermediate pressure. It’s made up of a first stage body, yoke, dust cap, and ports/port plugs. Now you know the basics of a scuba diving regulator first stage!

Understanding the Primary Second Stage of a Scuba Regulator

What is it?

The primary second stage of a scuba regulator is the part of the regulator that a diver actually breathes from. It reduces the pressure of the air coming from the regulator hose to a pressure that a diver can safely breathe. It’s one of two second stages on a standard open-water-style regulator.

What Does it Do?

The primary second stage of a scuba regulator has a few key functions:

  • Purge Button: This is the button on the face of the regulator that allows you to flood the second stage with air and push out any water that’s gotten in.
  • Ease of Breathing Adjustment: This lever or knob lets you adjust the breathing resistance to prevent free flow (when air flows rapidly out of the regulator without you breathing from it).
  • Exhaust Valve: This plastic unit channels your exhaled air bubbles away from your face.
  • Mouthpiece: This is the part of the regulator that you bite down on. It’s usually made of silicon or soft rubber and comes in a variety of shapes and sizes. It’s removable and replaceable.

How to Use it

Using the primary second stage of a scuba regulator is easy:

  • When you’re getting ready to dive, make sure the breathing resistance is set to “pre-dive” to prevent free flow at the surface.
  • When you’re underwater, adjust the breathing resistance to “dive” for easy breathing.
  • If your regulator gets filled with water, use the purge button to get rid of it.
  • Make sure your mouthpiece is secured with a zip tie or cable tie so it doesn’t slide off during a dive.
  • Enjoy your dive!

What is an Alternate Second Stage?

What It Does

An alternate second stage is like a life-saving sidekick! It does the same job as a primary second stage, but it’s only used in an emergency situation when a diver runs out of air. With an alternate second stage, a diver can help out an out-of-air buddy without putting himself at risk.

The Parts

Here’s a breakdown of the parts of an alternate second stage:

  • Mouthpiece: This is the part of the regulator second stage that a diver bites down on. It should be a standard size so any diver can use it in an emergency.
  • Low-Pressure Hose: This transports air from the regulator first stage to the second stages. An alternate second stage’s LP hose is usually longer than the primary second stage’s, so it’s easier for an out-of-air diver to use. It’s usually a bright color, like yellow, so it’s easy to spot in an emergency.
  • Purge Button: This has the same function as the primary second stage’s purge button – to remove water that has entered the second stage. Alternate second stage purge buttons are usually brightly colored, so they’re easy to find in an emergency.
  • Ease of Breathing Adjustment: This can be used to increase or decrease breathing resistance during a dive. If it’s present, it should be adjusted so the alternate second stage has increased breathing resistance. It should also be turned to “pre-dive” to make sure it doesn’t free-flow during the dive.

Where to Attach It

An alternate second stage should be attached to the Buoyancy Compensator (BC) or diver somewhere between the bottom of the chin and the lower corners of the rib cage. That way, it’s easy to access in an emergency.

Everything You Need to Know About Scuba Regulators

What Does a Scuba Regulator Do?

Ever wondered how scuba divers can breathe underwater? Well, it’s all thanks to the scuba regulator! This nifty device takes air from your scuba tank and reduces the pressure so it’s easy to breathe. It then delivers it to you so you can explore the depths of the ocean.

Yoke vs DIN Connectors

When it comes to scuba regulators, there are two main types of connectors: Yoke and DIN. The Yoke connector is like a clamp that attaches to the outside of the tank valve, while the DIN connector screws into the inside of the tank valve.

What’s the Purpose of a Scuba Octopus?

If you’re ever in an out of air situation, a scuba octopus is your best friend! It’s a backup scuba regulator that you can hand over to your dive buddy so they can get to the surface. Plus, if anything goes wrong with your primary regulator, you can switch over to your scuba octopus.

What Are the First and Second Stages?

The first stage on your scuba regulator is the part that lets air flow from your tank into your hose. It regulates the air flow and reduces the pressure so you can breathe easily. The second stage further regulates your air flow and contains your mouthpiece. Some models even have an adjustment knob so you can control how easy or hard it is to breathe underwater.

So there you have it! Now you know all about scuba regulators and how they help you explore the depths of the ocean. Time to get out there and dive in!


As you can see, a regulator is the most important piece of diving equipment. It’s the lifeline between YOU and YOUR air source and makes breathing underwater possible.

So don’t forget to pack yours before your next dive!

Joost Nusselder, the founder of Kauai Surf Report is a content marketer, dad and loves trying out new sports with everything surfing at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2019 to help loyal readers with surfing and water sporting tips.