Testing Your Home for Asbestos

If you live in a house built before the 1980s, there is a fair chance something in it contains asbestos: the ceiling texture, the floor tile and the black glue under it, the joint compound in the walls, the siding, the old furnace or pipe insulation in the basement. Most of the time that material does no harm sitting where it is. It becomes a problem when it is sanded, scraped, cut, torn out or broken, because that is when fibers get into the air.

You cannot tell asbestos by looking at it. The only way to know whether a material contains asbestos is to have a sample analyzed by a laboratory. This page explains which materials are worth asking about, who should take the sample, how the lab tests it, and what the report means.

A test of your house is not a test of you. If you are worried about asbestos you breathed years ago at work or at home, a material test cannot answer that. A chest X-ray read by a certified B-reader can look for the scarring asbestos leaves; see I was exposed to asbestos. And if you or someone in your family has already been diagnosed with mesothelioma, lung cancer or asbestosis, call us.

Materials worth asking about

Asbestos went into thousands of building products, most heavily from the 1920s through the 1970s. Some products kept it into the 1980s, and stock already made could be installed after a ban. These are the materials found most often in homes:

• Popcorn and textured ceilings. Spray-on acoustic ceiling texture often contained asbestos. Spraying asbestos on for decoration was banned under the Clean Air Act in 1978, but ceilings already sprayed were left in place. See Asbestos in joint compound, popcorn ceilings and paints.
• Drywall joint compound and patching compound. The Consumer Product Safety Commission banned asbestos in consumer patching compounds in a rule issued in December 1977; the ban took full effect in mid-1978. Walls finished before then, and some finished shortly after, may have asbestos in the seams and texture. See joint compound.
• Floor tile, sheet flooring and black mastic. Nine-inch-square tiles are the classic warning sign, but vinyl-asbestos tile came in other sizes too, and the backing of sheet vinyl and the black adhesive underneath can contain asbestos on their own. See Asbestos in floor tile and black mastic.
• Vermiculite attic insulation. Loose, pebbly gray-brown or gold insulation is often vermiculite, much of it from the mine at Libby, Montana, sold as Zonolite. EPA advises treating it as if it contains asbestos and leaving it undisturbed; a standard lab test can miss the asbestos in it (see below). See Libby vermiculite.
• Pipe, boiler and furnace insulation. White or gray wrapping on old heating pipes, the insulation on a boiler, and the tape on old ductwork are among the materials with the most asbestos in them. See Asbestos pipe and boiler insulation and Asbestos insulating cement.
• Siding, roofing and cement board. Asbestos-cement shingles, siding and flat panels are hard and stable until they are broken or cut. See Asbestos in cement shingles and Transite.
• Other places. Old plaster, window glazing putty, caulk, fireplace panels and artificial embers, and the paper backing behind some flooring and walls. See Asbestos in paper products.

Two of our posts walk through older houses room by room: Would a house built in the 1920s have asbestos? and Do homes built in 1910 have asbestos?

Leave it alone, or test it?

Material in good condition that you will not disturb is usually best left alone. That is EPA's advice for homeowners. Asbestos causes harm when its fibers are breathed in, and fibers are released when the material is damaged or worked on, not when it sits intact.

Test, or treat the material as asbestos, when:

• you plan to remodel, sand, drill, cut or demolish anything that might contain it;
• a material is crumbling, water-damaged, torn or flaking;
• you are about to replace flooring, a ceiling, siding or an old furnace; or
• a contractor needs to know before starting work.

If a material is damaged and you are not sure what it is, keep people and pets away from it, and do not dust, sweep or vacuum the debris.

Who should take the sample

EPA recommends a trained and accredited asbestos professional, and says taking samples yourself is not recommended. Many states license asbestos inspectors, and an inspector trained under the federal Model Accreditation Plan has taken the same course required for inspecting schools under AHERA. Ask whether the inspector is licensed in your state.

Hire an inspector who does not also do the removal. EPA advises against using the same firm to test and to remove, because a contractor who profits from the removal has a reason to find more asbestos.

If you take a sample yourself, many labs accept homeowner samples and mail-in kits are sold for this. The kit does not make sampling safe; you are still breaking into the material. Precautions described in older EPA guidance and by state health departments include:

• shut off heating and air conditioning and keep others out of the area;
• wet the material with a fine water mist before cutting into it;
• take a small piece through the full depth of the material (all layers) with a clean tool, and seal it in a container or zip bag;
• wear disposable gloves and a respirator rated for asbestos (a dust mask is not enough);
• patch the sampled spot, and wet-wipe the area and tools afterward.

How the lab tests a sample

Bulk building materials are tested by polarized light microscopy (PLM). The analyst looks at the sample under a microscope that uses polarized light to identify the asbestos minerals by their optical properties, and estimates how much is there. Most labs follow EPA's bulk-sample methods, including EPA Method 600/R-93/116 (1993). See bulk sample analysis.

Use an accredited lab. In the United States, the federal accreditation for labs that analyze bulk asbestos samples is the National Voluntary Laboratory Accreditation Program (NVLAP), run by the National Institute of Standards and Technology. It is required for school samples, and you should ask for it. Some states have their own approval programs as well.

Floor tile, mastic and roofing can fool PLM. In tile, mastic and other materials where the fibers are locked in vinyl, asphalt or resin, the fibers can be too fine or too hidden for a light microscope. A lab can confirm a negative PLM result with transmission electron microscopy (TEM). New York, for example, requires a TEM check before such a material is called asbestos-free.

Vermiculite is hard to test. The asbestos in Libby vermiculite is a small, unevenly spread fraction of the insulation, and standard lab tests can miss it. EPA says testing is not needed: treat vermiculite insulation as if it contains asbestos and leave it alone.

Air tests are a different test. An air sample measures fibers in the air, not what a material contains. Phase contrast microscopy (PCM) counts all fibers of a certain size and cannot tell asbestos from other fibers; TEM identifies asbestos. After a removal job, clearance air testing checks that the work area is clean before it is reopened. See How we measure asbestos in air.

Reading the lab report

A bulk report lists each sample, the layers the lab found in it, and for each layer the asbestos type and amount.

• "None detected" (ND). The analyst found no asbestos in what was tested. It applies to that sample only, and for floor tile and mastic it is stronger when TEM confirms it.
• A percentage and a type. For example, "Chrysotile 5%." Chrysotile is the type found in most building products; amosite and crocidolite turn up in some insulation and cement products. See The six types of asbestos.
• "Trace" or "less than 1%." Asbestos was seen, but below one percent. Federal rules define an asbestos-containing material as one with more than 1% asbestos, and when a lab's visual estimate is under 10%, the federal Clean Air Act rules, for the buildings they cover, require a more exact point count to confirm whether the material is over or under 1%.

One percent is a regulatory line, not a safety line. It decides which rules apply to removal and disposal. It says nothing about whether breathing the dust from that material is safe, and worker exposure limits apply however little asbestos the material contains.

Each layer counts. A wall can test negative in the drywall and positive in the joint compound or texture. Floor samples often show a clean tile over an asbestos mastic.

If the result is positive

You have three basic choices, and a professional can tell you which fits:

• Leave it in place if it is in good condition and you will not disturb it.
• Encapsulate or enclose it: seal it with a coating (encapsulation) or cover it (new flooring laid over old tile, for example).
• Have it removed (abatement) by a licensed contractor, especially before demolition or a remodel that would break it up.

Federal Clean Air Act removal rules (NESHAP) generally do not cover a house or a building with four or fewer homes, but state and local rules often do, including permits, notice before demolition and how the waste must be bagged and disposed of. Contractors working on your home must follow OSHA's construction asbestos rules for their workers. Check with your state's environmental or health agency before starting.

Buying, selling or moving

No federal law requires an asbestos test before a home is sold. Some states and cities require an asbestos survey before demolition or major renovation, and seller disclosure forms in many states ask about hazards the seller knows of. If you are buying an older home and plan to remodel, an asbestos inspection of the materials you will disturb is worth having before you close.

Asbestos you may already have breathed

Testing tells you about the materials in your house today. It cannot tell you about exposure from years ago: from a job in a shipyard, a plant or the building trades, or from take-home dust on a parent's or spouse's work clothes. Asbestos diseases appear decades after the exposure. If you worked around asbestos, see I was exposed to asbestos for what a screening can and cannot show. If you have been diagnosed, the companies that made and sold the asbestos may owe you compensation, and many of them have set up trusts to pay claims.