The key to reducing off-gassing odor is ventilation and time. Give your mattress plenty of time to air out in a well-ventilated room. This ensures your bed can release the majority of its off-gassing odor before you sleep on it for the first time. Many new mattresses need at least a few hours to air out. You can increase airflow in your bedroom by opening windows or using fans to help speed up the release of off-gassing odors.