Spare Air: A Professional’s Edge When Seconds Matter

You’ve probably seen it. That sleek little tank with the bold promise: “Your backup air in an emergency.” It’s called Spare Air, and yes — it can save your life. But it can also put you at risk if you don’t fully understand what it is and how it should be used. So let’s set the record straight — because when you’re underwater, clarity is everything.

💡What Is Spare Air?

Spare Air is a compact scuba tank designed to give divers a few precious breaths in an emergency. It holds 3.0 cubic feet of compressed air and delivers it through a built-in regulator.

The Spare Air Model 300 holds 3.0 cubic feet of compressed air, and the number of breaths it provides can vary depending on factors like depth, stress, and the diver’s breathing rate.

At the surface, a typical diver’s breath volume is about 0.5 liters (0.03 cubic feet) per breath. The Spare Air 300 should provide around 100-120 breaths at the surface. However, keep in mind at depth, your air consumption increases due to the pressure, so the number of breaths you can take decreases. 

The 3.0 cubic feet would last for roughly 30-40 breaths at 33 feet (10 meters) deep, where pressure is twice that of the surface. This means the Spare Air 300 is only intended for emergency ascents, where you need just a few extra breaths to safely make it to the surface.

🚨 Spare Air is not a toy or a gimmick. Spare Air is a real piece of scuba gear, used by military divers, commercial divers, and recreational divers worldwide as a last line of defense. And should only be used as such! 🚨

💥Spare Air is an Emergency Device

Spare Air is intended as an emergency device only! It can be a life saver in moments of emergency for example when you run out of air at depth, your buddy is too far or can’t assist or your regulator fails and you need to surface — now.

In these situations, Spare Air can give you 30 to 60 seconds of air to make a safe, controlled ascent. That’s not just helpful — that’s everything.

🚫 Spare Air is not a recreational toy! 

Spare Air is NOT for snorkeling. It is NOT for freediving. And it is NOT a toy.

Spare Air delivers compressed air at depth and breathing compressed air, even just a few feet below the surface, can cause:

💥 Lung over-expansion
🧠 Arterial gas embolism
🛑 Serious, even fatal injuries

These aren’t "maybe" risks-they are real and well-documented. Divers get trained for a reason.

People often visit the store and ask about using Spare Air for Free Diving or Snorkeling. This is not only not recommended, it can be very dangerous! 

🛑 Can I use Spare Air for Freediving?

One of the most common comments I hear from shoppers is that they will bring the Spare Air with them for freediving. 

STOP! DON'T! 

We get it — it seems like a great idea. “One more breath” underwater? Sounds awesome. But using Spare Air while freediving is like lighting a match next to a gas tank. Freediving is about breath-hold from the surface. Breathing compressed air mid-dive is a huge no-go — full stop.

Using Spare Air for Freediving breaks the most important rule of freediving. You never breathe compressed air at depth and then ascend.

When you breathe compressed air underwater (even from a small tank like Spare Air), nitrogen enters your bloodstream. If you ascend on a breath of compressed air (as you would when freediving), your lungs expand — and without proper exhalation or decompression, this can cause Lung overexpansion injuries, Arterial gas embolism, or Decompression sickness (DCS).

🚫 Spare Air is only for SCUBA

Even though it’s small, Spare Air is still SCUBA as it provides air at ambient pressure, just like a regular scuba tank.

Freediving relies solely on holding your breath from the surface, without breathing gas at depth. Using Spare Air during a freediving introduces serious risks to your body.

If you're ever in doubt: If you breathe compressed air at depth, you must ascend like a scuba diver — slowly, controlled, and with decompression in mind.

🚫 Spare Air Isn't for Snorkeling or Swimming

Spare Air is a SCUBA Device! Even though it’s small, it’s still compressed air at high pressure (3000 psi). That makes it part of the scuba family, and it carries the same risks. If someone breathes from it underwater — even just a few feet, they can experience injuries like lung over-expansion injury,  arterial gas embolism (AGE) or barotrauma. Even at depths as shallow as 1.2 meters (4 feet), this is possible!

Snorkelers or swimmers might think it’s a quick, safe breath but without scuba training, they might hold their breath on ascent  or use it repeatedly at shallow depths increasing nitrogen risk; and not understand the refill, care, or pressure involved.

If you're snorkeling and want to stay underwater longer or feel safer, consider investing in a high-quality snorkel and mask (dry snorkels are great), freediving gear (long fins, low-volume masks, proper training), snorkel vests or freediving floats for surface rest/support. And most importantly training on breath-hold techniques for longer bottom time, safely

💡 When Should You Use Spare Air?

Spare Air is intended for use by certified scuba divers as a backup air source. It is intended for use in emergency rescue scuba situations such as out of air. It is not intended for shore dives, lake diving or as a replacement for proper SCUBA equipment. 

💡 What Air Should You Use?

If you decide to purchase a Spare Air you need to follow the protocols to safely and properly refill your tank. Spare Air uses normal compressed air, NOT pure oxygen. Pure O₂ under pressure is dangerous.

Spare Air units are filled with compressed atmospheric air, not pure oxygen. Atmospheric air is about 21% oxygen, 78% nitrogen, and trace gases. That’s the same as what’s in a scuba tank unless it's specifically filled with Nitrox or Trimix.

We do not use Pure Oxygen as Pure O₂ becomes toxic at depth. Oxygen toxicity can occur at partial pressures above 1.6 ATA — which you reach at just 6 meters (20 ft) on 100% O₂.  Pure O₂ under pressure carries a huge risk of fire or explosion as O₂ can combust with even small traces of oil or contaminants in the tank or valve.

Always use clean, dry, filtered compressed air, rated for breathing — same as what you'd put in a regular scuba tank. You can fill your tank by using a scuba tank, a dive shop’s compressor (which uses filters), or a portable compressor with the right filtration system for breathing air

💡How Do You Refill Your Spare Air?

The most common and quickest method to refill your Spare Air is from a SCUBA Tank. You will need  the 910S Tank Refill Adapter which is included in the kit. 

💡 Refilling your Spare Air from a SCUBA Tank Steps:

1. Remove the protective cap from the check valve on your Spare Air.
2. Thread the 910S adapter onto the check valve port.
3. Connect the adapter to your filled SCUBA tank.
4. Slowly open the SCUBA tank valve to allow the pressure to equalize and fill your Spare Air.
5. Once filled, close the SCUBA tank valve and disconnect the adapter.
6. This process typically takes about one minute.

If you don't have access to a SCUBA tank, many dive shops can refill your Spare Air using a compressor. You will need the 920C Air Compressor Refill Adapter (not included)

💡Refilling your Spare Air at a Dive Shop Steps:

1. Thread the 920C adapter onto the check valve port of your Spare Air.
2. Attach the compressor whip to the refill adapter.
3. The dive shop will then fill your Spare Air to 3000 psi.
4. Ensure the dive shop uses purified, dry compressed breathing air for safety. 

If you would like to use an air compressor, you will need to purchase the Nomad III compact air compressor and the 930C Custom Air Compressor Refill Adapter. This method allows you to refill your Spare Air from home, a boat, or any location with access to the compressor. 

If you prefer a manual method, you can refill your Spare Air using a high-pressure hand pump. You will need to purchase the SA930C refill adapter. This method is portable and doesn't require electricity, but it does require physical effort. 

🚨 Tips for Safe Refilling 🚨

1. Use Only Clean, Dry Air: Always ensure the air used for refilling is purified and dry to prevent contamination.
   
   
2. Check the Pressure Indicator: The standard pressure indicator pin should be flush with the surface when full. If you have the optional dial gauge, it should read 3000 psi.
   
   
3. Regular Maintenance: Store your Spare Air full or with positive pressure to prevent contaminants from entering. It's recommended to replace the air annually and have the unit serviced regularly.

💡 Spare Air: Tool or Trap?

Spare Air is a great tool — for the right diver, in the right situation.

But if you’re looking to stay underwater longer while snorkeling or freediving, there are safer, smarter options. Don’t let a misunderstanding turn this life-saving device into a liability.

The Spare Air Model 300 is valued by many divers as a compact, emergency air source, particularly for shallow recreational dives. However, potential buyers should be aware of its limitations in capacity for deeper dives and ensure proper maintenance to prevent issues.

Want help choosing gear that matches your dive style — whether it’s scuba, snorkeling, or freediving? Come see us at Xico Dive Shop. We’ll get you the right equipment for your adventure — and show you how to use it the right way.