Expansion Chamber
Overview
An expansion chamber is an air-system component designed to give liquid CO₂ space to expand into gas before entering the marker’s valve system, improving consistency and reducing pressure spikes during firing.
Key Points
- Used primarily on CO₂-based markers before the widespread shift to compressed air.
- Allows liquid CO₂ to expand into gas, smoothing pressure delivery.
- Reduces velocity spikes, freeze-ups, and inconsistent shot performance.
- Often mounted on the marker’s foregrip or inline with the air source.
- Less common in modern play due to compressed air replacing CO₂ in competitive formats.
- Still found on older markers, certain rental fleets, or budget setups.
Details
An expansion chamber is a foregrip-like component added to CO₂-powered markers to improve the transition of liquid CO₂ into usable gas. CO₂ is stored as a liquid under pressure, and if that liquid enters the marker’s internal valve system, it can cause freezing, erratic velocities, or extreme pressure spikes.
The expansion chamber provides additional internal volume where liquid CO₂ can absorb heat from the environment and convert into gas before reaching the regulator or valve. This stabilizes pressure and creates more predictable shot behavior.
Prior to the rise of compressed air (HPA), expansion chambers were common upgrades. Modern markers overwhelmingly use compressed air systems, which deliver stable, dry, non-liquid gas. As a result, expansion chambers are now uncommon in competitive paintball but remain relevant for older markers, recreational setups, or scenarios where CO₂ is still used.
While expansion chambers provide improvements, they do not fully match the stability of a regulated compressed air system. Their function is tied to ambient temperature, player rate of fire, and tank orientation.
Understanding expansion chambers helps players maintain older equipment and recognize legacy technology still present on some fields.
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