Oil-based paints release volatile organic compounds (VOCs) into the air as they dry, which can be harmful to people with respiratory issues and can contribute to air pollution. For this reason, it is generally recommended to use oil-based paints only in well-ventilated areas or outdoors. If you do need to use oil-based paints indoors, be sure to open windows and doors to allow for proper ventilation, and consider using a respirator to protect yourself from inhaling the VOCs.