UV light air purifiers can be safe if they are used correctly and have been properly tested and certified. The UV-C light used in these purifiers is effective at killing bacteria, viruses, and other airborne pathogens. However, prolonged exposure to UV-C light can be harmful to humans and pets, and it's important to follow the manufacturer's instructions for safe use. It's also essential to remember that UV-C light air purifiers are not a substitute for regular cleaning and disinfection, and should be used in conjunction with other air purification methods.