Gas are based on moths. They have blue robotic bodies with a pair of black eyes, small yellow wings, and a V-shaped yellow brow on their foreheads.
In Sonic the Hedgehog CD, Gas appear as enemies in Collision Chaos. In gameplay, Gas appear in groups and exhibit patterns similar to the Pata-Batas. More precisely, they can only fly forward in a zig-zag pattern. As they fly around however, they leave behind a trail of sparkling dust that does not seem to affect the playable character. However, the Gas can still damage the playable character when making physical contact with them. In the Bad Future or sometimes in the present timeframes, where they have broken down due to age and leaving them with pierced wings, the Gas do not leave a trail of sparkling dust as they fly and move around at slower paces.