It is generally ok to leave a dehumidifier on overnight or when no one is home, as long as you follow some basic safety guidelines. Firstly, it's important to make sure that the dehumidifier is placed on a stable surface and is not blocking any vents or air circulation. This will help prevent the unit from overheating or tipping over. Additionally, you should ensure that the dehumidifier is not placed near any flammable materials, such as curtains or papers, as this can increase the risk of fire. It's also a good idea to periodically check the dehumidifier to make sure that it is working properly and that the water collection tank is not full, as a full tank can cause the unit to shut off or overflow. The dehumidifier's electrical cord and plug should always be in good condition, and it should always be plugged into a grounded outlet. Overall, it is generally safe to leave the dehumidifier on overnight or when no one is home as long as you follow these fundamental safety precautions and regularly check the appliance.