Knob and tube wiring is an older type of electrical wiring that's no longer used and generally not considered safe. However, some homes still have it, or may have a knob and tube wiring system that was incorrectly modified or rigged to work with a modern electrical system. Knob and tube wiring may contain asbestos insulation, but the only way to know is to have the material professionally tested.

Yes, even a single, one-time exposure to asbestos can be harmful and increase the risk of future illness, including certain diseases and cancers. The level of risk depends on several factors, such as the concentration and intensity of the exposure. A small, brief exposure is less likely to cause significant damage than an exposure to a high concentration of asbestos fibers.

The likelihood of developing severe health issues increases with repeated or prolonged exposure. Individual reactions to asbestos vary; some people may have multiple exposures without harm, while others are more susceptible. Asbestos-related illnesses may not manifest for 10 to 40 years after inhalation.

Due to these risks, it is crucial to take precautions. Personal protective equipment (PPE) may not offer complete protection, as fibers can get through small gaps. The EPA recommends hiring a professional for testing and removal if you suspect the presence of asbestos in your home. If you are concerned about a potential exposure, consult your doctor.

If you know your popcorn ceiling has asbestos, you should not attempt to clean it. It simply is not possible to learn how to clean asbestos safely without potentially releasing microscopic fibers into the air that could lead to severe illness in the future. Avoid disturbing or cleaning the ceiling until the asbestos removal company can get rid of the popcorn ceiling.

Depending on the size of your home, the inspection process could take a few hours or a few days. While inspecting your home, the asbestos specialist will take small sections of the potentially contaminated material. They will then send the sample to an accredited laboratory or the local health department for testing. 

The cost of asbestos testing depends on your location, the home's size, and the testing area's complexity. Plan to spend between $230 and $800 for testing. During testing and while handling potential asbestos, the specialist may wear protective gear, including gloves, overalls, appropriate footwear, and respiratory equipment.