Look for someone that has a background check available, great references and great organization skills to decrease the stress.
Yes, they should let you know for sure. You could bring those into your own home trough your vacuum, cleaning rags and cleaning supply basket, bed bugs are a very hard to get rid of pest and you should know if they are around ahead of time.
It depends on what you are trying to accomplish, the air purifier will take care of germs and the dry air from your heat, the oil diffuser on another hand will provider, better breathing, great scent or a calmer atmosphere.
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