Removal of asbestos coating from pipes and ducts

In old houses built between the late 1920s and late 1970s, it is common to find asbestos cladding on boiler pipes and ducts. If your home was built during this time, you may find some even if the house or property has been renovated. If the basement is finished, it may be that the asbestos coating is hidden in the walls and you are not even aware of it.

As long as asbestos is sealed, it is not harmful to you and your loved ones. However, if you plan to make renovations or if you need to have your heating, ventilation or air conditioning system repaired or replaced, then this is a problem and you will have to remove it.

Identification of asbestos coating on pipes and ducts

The coating comes in the form of a paper-like material and has the same characteristics as plaster. In some cases, it looks like a textile that wraps around it. In older houses, ducts and pipes were completely covered with asbestos, while later only the elbows and joints were covered with it. Asbestos siding can even extend to where the floor vent is located. This poses a greater threat because the fibers can be touched, released into the air and easily inhaled.

Use of asbestos coating

Asbestos was used as insulation to cover pipes and ducts. Due to its heat resistance properties, its insulating efficiency has proven to be very high. Because of the high heat in the ducts and pipes, something was needed that could hold up.

Asbestos coating placed on the outside of heating ducts is less likely to release fibers into the duct because it creates positive pressure. What is concerned, in fact, is who resides in the area where asbestos is present. However, asbestos coating on the outside of the return ducts is a greater threat because it creates negative pressure and if the duct is damaged, fibers can be released and spread throughout the home.

In cases of asbestos removal, hard asbestos is usually handled according to a number of safety procedures (area signage, insulation, dust control, protective equipment, etc.) and with a bag-glove method, as well as the wetting and cleaning of exposed metal surfaces and the sealing of clean surfaces.

What to do with asbestos coating?

Option 1: Leave the asbestos paper coating in place, possibly coated or spray sealed

The best practice is not to touch the exposed material unless other construction conditions or very poor conditions require its removal by a professional. Some asbestos contractors use an aerosol encapsulation product or paint where the paper coating is to be left in place.

As long as the asbestos paper remains outside the supply ducts, which are normally under neutral or positive air pressure, the chances of asbestos from the paper entering the duct system and the building air remain minimal. If, on the other hand, asbestos-containing materials are found inside the duct system or air handler, this would be a different and more serious concern.

Option 2: Remove asbestos paper coating from the ducts, and consider a complete duct renovation

If it is necessary to remove the seal or insulation from a duct covered with asbestos paper for other reasons, such as renovations, reconstruction or damaged, exposed or friable materials, the removal is carried out in accordance with asbestos decontamination precautions.

More often than not, it is much cheaper and easier to completely remove the intact duct from the building than to try to remove only the paper coating followed by cleaning the duct. In summary, in most cases, it will be easier and cheaper to remove old asbestos-coated ducts and replace them with new ducts in the same place (if the ducts are still needed) than to try to clean and reuse the old ducts.

Treat materials as MPCA, i.e. materials presumed to contain asbestos

This material must be reasonably treated as “material presumed to contain asbestos” or “MPCA”. “Hardened” asbestos paper and paper tape were used to seal air leaks and to lightly cover metal heating ducts that generally dated before 1965 but may have been used until about 1981.

Current flame retardants to replace paper or asbestos materials used in HVAC ducts

If an application requires a flame retardant sealing material, it is possible to replace the asbestos material and even the asbestos paper interlining, i.e. the flame retardant sealing tape for ducts, and the asbestos tape (duct seal) used for high-temperature operations with a watertight, chemical-, non-combustible (and ozone-resistant) Hi-T silicone tape, which is carbon-resistant and airtight and can be used to connect the duct cable to the ventilation pipe.