The gas channel layout has an influence on the part filling pattern and on the propagation of the gas bubble. The unfavorable cavity is not filled in concentric circles from the gate. Instead, the gas channel promotes resin flow and directs material into designated areas. A favorable method is to direct flow towards the end of fill. In this fashion, when gas is injected into the part, the gas pushes the material outwards and fills the cavity. If the gas bubble inside the gas channel ends before the cavity is filled, gas fingering or blowouts are likely to occur. This is due to the small volume of material in front of the gas bubble, creating low resistance, and allowing gas penetration into the thin wall.

Each gas injection point should contribute to one gas channel. Closed loop or intersecting gas channels should be avoided or displaced material will deadhead in between the gas channels that run together creating material accumulations. These material accumulations can create sink marks. Gas channels that are due to intersect should taper off and end short of running into one another. Sometimes these intersecting gas channels can create weld lines and in larger gas channels, race tracking can occur, thereby trapping gas or creating flow lines. It is advisable to use smaller gas channels in order to avoid race tracking.

The benefits of gas injection can be employed on a product that requires a ribbed structure. Some of the benefits include improved flow characteristics, improved rigidity, and reduction of sink marks. As shown in the below picture, gas channels are cut at the base of the ribs. Bosses can also be integrated into the structure without sink marks on the visible surface.

Gloss level changes occur in some materials when gas channels are utilized. It is sometimes necessary to add a textured surface to the visible surface to hide witness lines.

The following picture shows a paper feeder for a copier. A cold runner feeds material into a gas channel. The gas channel acts as an internal runner by promoting flow through the part. In some cases, a hot runner system may not be needed because the gas channel acts as a resin flow channel. Since gas is used to pack out the part, the gate is allowed to freeze without any adverse effects. The gas pressure packs out the part more uniformly than the injection molding machine pack and hold pressures would with a freezing gate. Therefore, gas injection reduces internal stresses and warpage is minimized.

When gas is injected through the machine nozzle, gas travels through the sprue and runner system before it enters the part. Material regrind weight of the cold runner is subsequently reduced because of the hollow channel that is formed during the process.