Blowing agents (also known as 'pneumatogens') or related mechanisms to create holes in a matrix producing cellular materials, have been classified as follows:

Polystyrene foams are produced using blowing agents that form bubbles and expand the foam.

High-density microcellular foams can be formed without the addition of blowing agents by mechanically frothing or nucleating the polyol component prior to use.

The isocyanate is usually added by itself and the polyol stream is usually more complex, containing catalysts, surfactants, blowing agents and so on.

Uses include refrigerants, blowing agents, propellants in medicinal applications, and degreasing solvents.

There are two main types of blowing agents: gases at the temperature that the foam is formed, and gasses generated by chemical reaction.

These blowing agents eventually leak out of the panels.

Several states have banned polystyrene that uses CFCs as blowing agents.

The majority use of hydrazine is as a precursor to blowing agents.

May use a variety of blowing agents.