Although made of breathable fabric, it is recommended to use SlumberPod in a well-ventilated and climate-controlled environment — as it is approved for indoor use. You can open one or more vents for overnight sleep (when parents are going to bed and lights are out) to increase airflow if needed. Dress your little one for possible + 1-2 degrees Fahrenheit difference inside SlumberPod. Also - In addition to passing all applicable juvenile safety tests, we had extensive tests done to include CO2 rebreathing by a third-party, independent lab. It was deemed low hazard with the vents closed.