If you’re getting into airsoft and you’re interested in picking up a gas powered airsoft gun, you’ll probably find yourself mired in the age-old debate between green gas and CO2.
A popular assumption among newer airsofters is that more power, and subsequently anything that gets you there, is probably your best bet.
But, and keeping in mind the old saying about making an assumption, that approach isn’t always ideal.
Both green gas and CO2 have their own characteristics that can have a drastic impact on gameplay and which is best really depends on the individual’s preferences and needs.
As a result, players need to really understand these two gasses and how their particular strengths and weaknesses can affect performance in different situations.
To help out, we’ve dived deeper into the topic, comparing green gas and CO2 in order to help users better decide which propellant is really best for their needs.
What Is Green Gas In Airsoft
The original airsoft gas, green gas is essentially propane gas mixed with a small amount of lubricating silicone oil and without the usual mercaptan that gives propane its characteristically unpleasant smell.
Green gas tends to come in largish bottles and users refill their magazines by pressing the bottle’s tip into their mag’s valve.
What Is Co2 In Airsoft
CO2, of course, stands for carbon dioxide, a well known gas that is commonly used in a variety of tactical hobbies and products, such as paintball, air pistols, air rifles, traditional BB guns and pellet guns, and is the second most widely used gas in airsoft.
CO2 is usually sold as small, pre-filled cartridges (usually 12g) that can be inserted into an airsoft magazine and then tapped to fill the mag with compressed gas.
CO2 is usually sold as a “dry” gas, with no silicone oil added to it.
Green Gas vs CO2: Compression and Power
Aside from their inherent differences in chemical composition, which may be of interest to more scientifically-minded airsofters but which won’t be discussed here, one of the most critical differences between green gas and CO2 relates to their relative compression and power output.
Broadly speaking, CO2 is compressed under far more pressure than green gas.
Green gas is generally pressurized at around 120 PSI or around 8 bar.
In contrast, CO2 cartridges are often compressed to around 900 PSI or about 62 bar, nearly 8 times the pressure of green gas.
As a result, airsoft guns running on CO2 tend to have a higher muzzle velocity as measured by FPS than their green gas counterparts and tend to be a little more consistent in power output after a few shots compared to green gas, which tends to suffer from power drop as gas is expended.
Curious to learn more about airsoft gases in general? Read more about it in our guide to airsoft gas.
Price Differences Between The Two Gasses
When it comes to pricing out green gas and CO2 there are a lot of factors at play.
A lot of it depends on where you guy your gas, any deals they may be running, availability, the efficiency of the airsoft gun in question, rate of fire and so on.
Typically, green gas is sold in a big bottle of some kind that can hold enough gas for somewhere between 1500-2000 shots, depending on the airsoft gun and its efficiency.
In the US these can cost around $15 or so with tax, meaning a shot can cost around a cent (1¢) or so.
Being something of a more specialized gas, green gas is most often sold in airsoft retailers.
That said, some users tend to run straight propane, which can lower the cost per shot even more.
In contrast, CO2 is contained in a disposable cartridge that fits into a magazine.
These are usually sold in a pack and, depending on where you shop, you can usually pick up a box of 15 cartridges for just under $15 and even bigger packs (30 or more) at a bulk discount.
And, because CO2 cartridges are used in everything from airsoft guns to pellet guns to some sporting airguns, they can be pretty much found at any sports retailer so you can really shop around for them (also being sold in more stores tends to mean that they are subject to more sales).
As a result, a single CO2 cartridge can often be picked up for well under $1.
CO2 airsoft guns tend to get somewhere around 50 – 70 shots per cartridge, meaning that the cost per shot can be something like 1.4-2 cents per shot.
Increasing the cost a little more is the fact that, because CO2 is sold in disposable cartridge form, if something goes wrong with a mag and you have to troubleshoot something, it often means you’ll have to waste a cartridge.
Again, there are a lot of variables to consider that can affect price, but generally speaking green gas tends to be a little cheaper per shot than CO2.
Which Is More Commonly Used In Airsoft Guns Green Gas Or Co2?
In general, when it comes to gas airsoft guns, there are more models out there that are designed to run on green gas than there are CO2.
With the exception of airsoft revolvers, which are nearly always CO2-powered, a larger number of gas airsoft pistols are designed to use green gas rather than CO2.
With gas airsoft rifles and SMGs this is even more true, with the vast majority of airsoft rifles being designed to use green gas.
Although many brands also make CO2 cartridges for these models, the quality of these mags can vary rather significantly.
As a result, it is more likely that you’ll find a good quality gas airsoft pistol or rifle in the style you like if you don’t mind using green gas.
Keep in mind that this isn’t to say that there are no good CO2 airsoft guns out there – in fact there are quite a few great ones around – but there tends to simply be more green gas options out there.
Benefits Of Green Gas
As mentioned above, running a gas airsoft gun on green gas can be a little cheaper than CO2.
It’s not a huge amount, it’s true, but if you plan on playing in longer games where you’ll be blasting out hundreds of BBs, it can add up over time.
Convenient to carry around
A single, decently-sized bottle of green gas can hold enough gas to fire off 1500+ shots. That means that players will generally only have to bring a single bottle to last them through even the longest and most high intensity of games.
In contrast a 12g CO2 cartridge is far more limited and can only hold enough gas for 50-100 shots or so, meaning players might have to take a whole bunch of small cartridges with them to a field, which can be kind of awkward and take up much needed space in a loadout.
Convenient to use in game
Because of the way green gas magazines and refilling works, it can be a lot easier to use a bottle of green gas compared to CO2.
Rather than having to remove, replace and puncture a CO2 cartridge (usually requiring the use of a tool), users simply refill a mag by pressing a bottle’s nozzle into its valve.
Similarly, using green gas means that players can top off their mags as needed, rather than having to scrap a whole cartridge if something goes wrong.
More usable in CQB and indoor games
Because green gas tends to produce a lower FPS rate compared to CO2, guns that use it tend to more easily squeeze under any FPS limits that a field might have, making it more useful for players who want to try their hands at CQB or indoor matches.
Less wear and tear on an airsoft gun
Because green gas is less pressurized, its action tends to be a little less stressful on an airsoft gun’s parts than CO2.
As a result, guns that run green gas tend to last longer and require fewer maintenance and repair than CO2 versions.
Requires less maintenance
Similarly, because green gas contains a bit of silicone lube, it tends to do a better job at keeping gas airsoft gun parts and seals lubed and therefore users can go for a little longer without doing routine maintenance than they would with a CO2 gun (users will, obviously, still need to clean and check their gun periodically).
More models designed for its use
Simply put, there are more high quality airsoft guns out there (particularly with rifles) that are designed to run on green gas than there are CO2.
Use of propane
Green is, essentially, propane that has been modified a bit and, as a result, most guns that run green gas can run on propane, as well.
Because (in the US, at least) propane tends to be sold in larger tanks, and can often be purchased quite inexpensively, it can further lower the cost of ownership and use.
Disadvantages Of Green Gas
A little less widely available than CO2
CO2 cartridges, which are widely used in a variety of sports and applications, are pretty widely available from a number of sports retailers (and digital retailers like Amazon) and, as such, can be subject to a greater number of sales and discounts.
In contrast, green gas is more limited to stores that carry airsoft equipment (and Amazon, obviously).
Those who love a hard-hitting airsoft gun can be disappointed by the fact that green gas tends to have a lower average FPS than CO2 out of the box.
More affected by cold weather than CO2
Being less pressurized, green gas doesn’t tend to work as well as CO2 in cold weather, suffering from more inconsistent power output and a lower FPS in general.
Benefits Of Co2
Higher FPS on average
One of the main reasons that people go for CO2 over green gas is its relative power output.
Simply put, airsoft guns running on CO2 gas tend to offer a higher FPS rate than those running on green gas, meaning they’ll hit opponents harder.
Better action on blowback models
In line with its greater power, another benefit of CO2 over green gas is that it can have a snappier and more impressive “kick” or blowback action if you’re using a GBB airsoft gun.
The increased force provided by the more pressurized gas can give these guns a more realistic and enjoyable feel for some users.
More consistent power output
As mags empty, CO2 cartridges tend to suffer from power drop a little less than green gas, meaning that they’re a little less likely to suffer from very noticeable FPS differences after firing off successive BB rounds.
Individual cartridges are small and easier to carry
Although users will probably have to carry a few CO2 cartridges if they plan on playing in longer games, and this can be a little more annoying than carrying a single big bottle, 12g CO2 cartridges are pretty small (about the size of your thumb) and are a lot easier to stuff into pockets, holsters and vests than an 8 inch by 4 inch (20cm x 10cm) bottle.
Better and more consistent performance in cold weather than green gas
Largely due to differences in pressurization, CO2 gas tends to outperform green gas in cold weather, suffering from less noticeable a drop in FPS and enjoying more consistent performance.
Can find CO2 cartridges at just about any sports store, often in bulk
CO2 cartridges are pretty widely used with BBs, airguns, pellets and more and can be found in pretty much any sports store online or in real life.
As a result, users can more frequently enjoy sales and are less likely to be affected by supply chain disruptions.
CO2 cartridges are also often sold in bulk. Depending on the retailer, users can easily buy 5, 10, 15, 30, 50, 100 or even 500 cartridges at a time.
Disadvantages Of Co2
Fewer shots per cartridge
Generally speaking a can of green gas can hold well over a thousand shots, while a CO2 cartridge may only hold enough gas for a few dozen shots.
Can fire too hot for some games and fields
CO2 airsoft guns do tend to hit hard, with a higher overall FPS output than their green gas counterparts.
While certainly fun, the downside to that is that they may not be usable when FPS restrictions are in place, such as CQB and indoor games where power output is kept under 350 FPS for safety reasons.
Because few CO2 airsoft guns chrono under 350 using 0.20g BBs, it means they may not always be field legal.
Increased wear and tear on airsoft guns
Another downside to CO2’s increased pressurization and power is that it tends to put a lot more strain on the airsoft guns running it.
As a result, CO2 airsoft guns tend not to last as long and tend to require more maintenance and repair to keep up with the increased wear and tear.
Relatively fewer models designed for it
Although there are a lot of CO2 airsoft guns out there, there are relatively fewer CO2 models compared to green gas, which means finding a high quality airsoft gun in the style you want can be a little more tricky and costly.
Can’t top up magazines on the go
Finally, because CO2 is contained in disposable cartridges, it means that, unlike green gas, you can’t simply top up a magazine on the go. If something goes wrong with a mag, or you want a quick refill halfway through a magazine, you’ll have to use a new cartridge.
Co2 Vs Green Gas Which Is Better For Your Needs?
With all the aboves pros and cons laid out, it can be a little hard for some users to figure out whether they should go with green gas or CO2 and it really boils down to what your needs and desires are as an airsoft player.
To help out, we’ve laid out some of the more salient considerations they should keep in mind below.
Green Gas Might Be For You If…
- You’d like the flexibility of playing in CQB and indoor games
- You live in an area where there are stricter FPS limits
- You are on a budget and are looking for the lowest cost per shot
- You don’t really enjoy doing frequent maintenance
- You would like to purchase and use cheaper airsoft guns
- You don’t want to carry a lot of mags or cartridges with you
- You live where it is warm and there’s not a lot of cold weather
Co2 Might Be For You If…
- You want a gas that will give you more power and better consistency when rapid firing
- You’re using a blowback airsoft gun and want it to have a good, solid kick
- You live where the weather is a lot colder throughout the year
- You aren’t concerned with FPS limits and mainly want to play outside
- You want to use an airsoft revolver
- You don’t mind, or actually enjoy, doing periodic inspection and maintenance
- You have the money to buy a good quality, durable airsoft gun
Can I use CO2 in my Green Gas Airsoft Mags (or vice versa)?
One thing that pops up from time to time in airsoft forums and discussions is whether you can just buy a green gas gun and run it on CO2 when you need the extra power or when it is cold out.
The answer is it really depends on the airsoft gun in question.
Traditionally, airsoft guns designed specifically for green gas aren’t really built to handle the increased pressure of CO2 gas.
As a result, they can experience rather serious problems when filled with a more pressurized gas, with slides cracking and breaking due to more forceful blowback, and even suffering from catastrophic failures in some cases.
Even those that initially fire well on CO2 will probably see a shortened lifespan due to the increased strain.
Conversely, filling a CO2 gun with green gas when it isn’t really built to accommodate it can result in the gun not having enough pressure to fire properly, with the green gas causing the gun to be prone to cycling problems, jams and other issues.
It is important to note that there are airsoft guns that have been designed to be able to run on both green gas and CO2 without suffering from performance or longevity problems.
These guns tend to have seperate green gas and CO2 mags available for them and they are (to some degree) becoming more increasingly common.
We found the ASG CZ P-09 to be an excellent example of such an airsoft gun, with a specifically designed slide and well-balanced construction that is light enough to reliably fire using lower-pressure green gas but durable enough to withstand CO2 mags.
At first glance, choosing between green gas and CO2 can seem like a no brainer – more power is better, right?
But, as with anything else, when you dig deeper into the matter you’ll often find that things are a little more complicated than that.
Green gas and CO2 both have their advantages and disadvantages and its important that airsofters understand these and consider their own needs before simply making a decision based on raw power.
David Lewis – A longtime airsoft and airgun enthusiast and collector, our editor David’s lifelong passion for tactical sports began in high school with some friends, a cheap knock-off airsoft M4, and an open field behind his parents’ house.
When he’s not plinking around, he enjoys sharing his knowledge of airsoft and helping those just starting out.