To inflate a heavy duty air mattress, first unroll and lay it flat on the ground. Locate the air valve and open it. Use a pump, either manual or electric, to fill the mattress with air until it reaches your desired firmness. To deflate, open the air valve and allow the air to escape. You can also gently press on the mattress to help push the air out. Once fully deflated, fold or roll the mattress and store it in its carrying case.