Are dusk diffusers safe?

Hello there, I'm curious about the safety of dusk diffusers. I've heard some conflicting opinions on whether they're SAFE to use or not. Could you please provide some insight into this matter? I'm particularly interested in knowing if they pose any health risks, and if there are any precautions I should take when using them. I appreciate your time and expertise on this topic. Thank you in advance for your help.