As we know Pascal's law which is also called Pascal's principle or the principle of transmission of fluid-pressure, states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted undiminished throughout the fluid.
The key expression is "incompressible fluid". We know that gases are more compressible as compared to solids and liquids due to larger inter-molecular spaces. An incompressible fluid cannot be compressed and has relatively constant density throughout. Fluid such as air can be either compressible or incompressible.
Generally, for theoretical and experimental purposes, gases are assumed to be incompressible when they are moving at low speeds--under approximately
Therefore, Pascal's Law can be applied to gases.