What does the insulation of asbestos wires look like?
Content
My article below will talk about what asbestos wire insulated wire looks like and give useful tips.
Asbestos wire insulation was a popular choice for electrical wire insulation during the 20s.th century, but production was discontinued due to numerous health and safety concerns.
Unfortunately, visual inspection alone is not enough to identify asbestos wire insulation. Asbestos fibers are too small и they not Yesn smell. You need to know what type of wire it is, when it was installed and where it was used for make an educated guess about the likelihood that the insulation contains asbestos. An asbestos test will confirm whether it is present or not.
I'll show you what to look out for, but first I'll give you a brief background on why determining the insulation of asbestos wires is so important.
Brief background information
Asbestos use
Asbestos was widely used to insulate electrical wires in North America from about 1920 to 1988. It has been used for its beneficial properties of heat and fire resistance, electrical and acoustic insulation, overall durability, high tensile strength, and acid resistance. When used primarily for general electrical wire insulation, a low iron form has been common in some residences. Otherwise, it was mainly used in places subject to high temperatures.
Concerns about the use of asbestos were first legally raised in the Toxic Substances Control Act of 1976 and the Asbestos Emergency Response Act of 1987. Although the US Environmental Protection Agency tried to ban most asbestos products in 1989, asbestos mining in the US ceased in 2002 and it is still being imported into the country.
Risks of asbestos insulation
Asbestos wire insulation is a health hazard, especially when the wire is worn or damaged, or if it is located in a busy part of the house. Chronic exposure to airborne asbestos fiber particles can accumulate in lung tissue and cause various diseases, including lung cancer, asbestosis and mesothelioma. Often symptoms do not appear until many years later.
Asbestos is now recognized as a carcinogen, so electricians no longer use it and seek to either remove it or replace it. If you are moving into an old house, you should check the wire insulation for asbestos.
How to identify asbestos insulated wiring
To help identify asbestos-insulated wiring, ask yourself four questions:
- What is the condition of the wire?
- What is this wire?
- When was the wiring done?
- Where is the wiring?
What is the condition of the wire?
If the wire, as you suspect, may have asbestos insulation in a damaged condition, you should still replace it. It should be removed even if it is not in use, but is in a room occupied by people. Look for signs of cuts, weathering, cracking, etc. If the insulation crumbles or falls apart easily, it can be dangerous whether or not it contains asbestos.
What type of wire is this?
The type of wiring can tell if the insulation contains asbestos. There are several types of wire with asbestos insulation (see table).
| Category | A type | Description (Wire with…) |
| Asbestos Insulated Wire (Class 460-12) | A | asbestos insulation |
| AA | asbestos insulation and asbestos braid | |
| AI | impregnated asbestos insulation | |
| AIA | asbestos impregnated insulation and asbestos braid | |
| Fabric asbolaked wire (class 460-13) | AVA | asbestos insulation impregnated with varnished cloth and asbestos braid |
| AVB | asbestos insulation impregnated with varnished cloth and fire-resistant cotton braid | |
| AVL | asbestos insulation impregnated with varnished cloth and lead coating | |
| Other | AF | asbestos heat-resistant reinforcing wire |
| CVA | asbestos insulation interlaced with armored cable |
The type of wiring insulation most concerns called vermiculite, sold under the brand name Zonolite. Vermiculite is a naturally occurring mineral compound, but the main source from which it was obtained (a mine in Montana) made it contaminated. It looks like mica and consists of silvery scales.
If you find this type of wire insulation in your home, you should call a professional to have it checked. Other brands of wire insulation containing asbestos include Gold Bond, Hi-Temp, Hy-Temp, and Super 66.
One type of asbestos wire insulation was a spray mold that created clouds of toxic fibers in the air. It would only be relatively safer if the insulation was properly sealed after spraying. Existing regulations generally allow no more than 1% asbestos to be used in sprayed insulation and bitumen or resin binders.
When was the wiring done?
The wiring in your house was probably installed when the house was first built. In addition to finding this out, you need to know when asbestos wire insulation was first used in your area or country and when it was discontinued. When did your local or national legislation prohibit the use of asbestos wire insulation?
As a rule, for the USA this means the period between 1920 and 1988. Homes built after this year may still contain asbestos, but if your home was built before 1990, especially between the 1930s and 1950s, there is a high chance that the wire insulation will be asbestos. In Europe, the cut-off year was around 2000, and around the world, asbestos wire insulation is still in use despite the WHO calling for a ban since 2005.
Where is the wiring?
The heat-resistant properties of asbestos-insulated wiring make it ideal for rooms subject to intense heat. Thus, the possibility of insulating wires with asbestos is high if the appliance is, for example, an old iron, toaster, stove igniter or lighting fixture, or if the wiring is otherwise near a heating appliance such as an electric heater or boiler.
However, "loose-fill" type asbestos wire insulation was also widely used in other places such as attics, interior walls, and other hollow spaces. It had a fluffy texture. If you suspect asbestos wire insulation in your attic, you should stay away from it, do not store things there, and call a specialist to remove asbestos.
A more easily identifiable type of asbestos insulation was boards or blocks glued to walls to hide wiring. They are made of pure asbestos and are very dangerous, especially if you see chips or cuts on them. Asbestos insulation boards behind wiring can be difficult to remove.
Asbestos test
You may suspect that the wire is insulated with asbestos, but an asbestos test will be required to confirm this. This includes taking precautions for potentially toxic hazards, and drilling or cutting to take a sample for microscopic examination. Since this is not something the typical homeowner can do, you should call in an asbestos removal professional. Encapsulation may be recommended instead of completely removing the asbestos wire insulation, depending on the situation.
Take a look at some of our articles below.
- Where is the engine ground wire
- How to disconnect a wire from a plug-in connector
- Can the insulation touch electrical wires
Links to images
(1) Neil Munro. Asbestos thermal insulation boards and problems of their removal. Retrieved from https://www.acorn-as.com/asbestos-insulating-boards-and-the-problems-with-their-removal/. 2022.
(2) Asbestos-contaminated vermiculite used for wire insulation: https://www.curriculumnacional.cl/link/http:/www.perspectivy.info/photography/asbestos-insulation.html
(3) Ruben Saltzman. New information about asbestos-vermiculite insulation of attics. Structure Tech. Retrieved from https://structuretech1.com/new-information-vermiculite-attic-insulation/. 2016.
