Where asbestos hides

Asbestos was used in so many products that it can turn up almost anywhere in an older building. Some uses are obvious, such as the white lagging on old steam pipes. Many are not: the adhesive under a floor tile, the joint compound in a drywall seam, the texture on a ceiling, the cement board behind a shower, the gasket in a valve. This lesson surveys where asbestos-containing material is found, explains the difference between friable and non-friable material, shows how building age guides suspicion, and describes why visual identification is never enough.

Friable and non-friable material

The most important property of an asbestos-containing material, from a safety point of view, is how easily it releases fibers. Friable material can be crumbled, pulverized or reduced to powder by hand pressure when dry. Non-friable material binds the fibers in a matrix such as cement, vinyl, asphalt or resin, so it releases few fibers unless it is broken, cut, sanded, drilled or ground. EPA's NESHAP rules divide non-friable material into Category I (packings, gaskets, resilient floor covering and asphalt roofing) and Category II (other non-friable material such as asbestos-cement products) and define regulated asbestos-containing material (RACM) to include friable material and non-friable material that has become or will become friable.

Friability is not fixed. Non-friable material becomes friable when it is damaged, weathered, burned or mechanically worked. A cement sheet that is intact releases little; the same sheet broken with a hammer or cut with a power saw releases large amounts. Damage, water and age can turn sound material into crumbling material, so the condition of the material matters as much as its type.

Common asbestos-containing materials

Building age as a guide

Building age is the first clue. Asbestos use in US construction was widespread from the 1920s to the late 1970s, and OSHA's construction standard treats thermal system insulation and surfacing material in buildings constructed no later than 1980 as presumed asbestos-containing material (PACM) unless it is shown not to be. Asphalt and vinyl flooring installed no later than 1980 must also be treated as asbestos-containing unless tested. Asbestos continued in some products after 1980, so a later building date reduces suspicion but does not rule asbestos out.

Age alone is not reliable for several reasons. Buildings are renovated in stages, so a 1995 building may contain a 1970s boiler or reused materials. Some products were made with asbestos for longer than others. Imported products have occasionally contained asbestos long after domestic use ended. And records are often incomplete. Age tells you how suspicious to be, not whether asbestos is present.

Residential versus commercial and industrial buildings

Houses and small apartment buildings most often contain asbestos in textured ceilings, drywall joint compound, vinyl flooring and its backing, vermiculite insulation, cement siding and roofing, furnace and boiler insulation, duct tape and wrap, and old plaster. Commercial, institutional and industrial buildings are more likely to contain sprayed fireproofing, extensive pipe and boiler insulation, acoustic plaster, ceiling tiles, asbestos-cement panels, roofing felts and industrial gaskets and packings. Industrial plants, refineries, mills, power stations and ships may contain large quantities of thermal insulation, refractory materials in furnaces and kilns, and asbestos textiles.

Why you cannot identify asbestos by looking

Asbestos-containing materials usually look identical to materials without asbestos. A white pipe covering may be asbestos, fiberglass, calcium silicate or mineral wool. A floor tile may or may not contain asbestos, and its adhesive may contain asbestos when the tile does not. Color, texture and the presence of visible fibers are not reliable guides. Only laboratory analysis of a sample, or reliable documentation from the manufacturer or a previous survey, can confirm whether a material contains asbestos.

Some clues raise suspicion: date of installation, product labels, manufacturer names known to have used asbestos, the fibrous appearance of certain insulations, and records from earlier surveys. Clues are reasons to test, not substitutes for testing. A competent person who suspects asbestos and cannot confirm otherwise should treat the material as asbestos-containing.

Hidden and unexpected locations

Many exposures happen because asbestos was hidden from view. Common surprises include:

• Insulation inside wall cavities, above suspended ceilings and in pipe chases, revealed only when the wall is opened.

• Multiple layers of flooring, with asbestos tiles and mastic buried under newer floor coverings.

• Asbestos-cement board behind tile in bathrooms, around fireplaces or behind wood stoves.

• Duct insulation, vibration dampers (the fabric joints in ductwork) and duct sealants.

• Debris left on top of ceiling tiles or in plenums from earlier removals or from deteriorating fireproofing.

• Old pipe insulation buried in crawl spaces or under slabs, and asbestos-cement pipe in the ground.

• Fire-rated doors, electrical panels and older appliances such as ovens and heaters.

This is why surveys must be thorough and why workers should stop when they uncover a suspect material that was not identified in the survey. Lesson 5 covers surveys, and Lesson 12 covers what to do when asbestos is discovered unexpectedly.

Condition assessment

Once asbestos-containing material is found, its condition determines how urgently it must be dealt with. Material in good condition that will not be disturbed can often be safely left in place and managed. Material that is damaged, deteriorating, exposed to vibration, water or physical contact, or located where work will disturb it, needs action: repair, enclosure, encapsulation or removal.

Using an inventory score

Building owners managing many materials often rank them by combining friability, condition and the likelihood of disturbance into a simple priority score. The scoring scheme below is illustrative; real programs use the method set by the owner's consultant or management plan.

# Illustrative priority scoring for asbestos materials in a building
FRIABILITY = {"non-friable": 1, "friable": 3}
CONDITION = {"good": 1, "fair": 2, "poor": 3}
DISTURBANCE = {"unlikely": 1, "possible": 2, "planned work": 3}

materials = [
    ("boiler room pipe lagging",   "friable",     "fair", "possible"),
    ("corridor floor tiles",       "non-friable", "good", "unlikely"),
    ("gym sprayed fireproofing",   "friable",     "poor", "possible"),
    ("washroom cement board",      "non-friable", "good", "planned work"),
]
ranked = []
for name, f, c, d in materials:
    score = FRIABILITY[f] * CONDITION[c] * DISTURBANCE[d]
    ranked.append((score, name))
for score, name in sorted(ranked, reverse=True):
    action = "act now" if score >= 12 else "plan" if score >= 3 else "manage in place"
    print(f"{name:28s} score {score:2d}  {action}")

gym sprayed fireproofing     score 18  act now
boiler room pipe lagging     score 12  act now
washroom cement board        score  3  plan
corridor floor tiles         score  1  manage in place

Even a non-friable material in good condition rises in priority when planned work will disturb it, because that is exactly when fibers are released. The score is a planning tool; it does not replace legal requirements to identify and control asbestos before work begins.

Industrial, marine and transportation settings

Industrial sites contain asbestos in places that rarely appear in building surveys. Refineries, pulp mills, smelters and power stations may have asbestos in high-temperature insulation on vessels, turbines and steam lines, in refractory linings of furnaces, kilns and boilers, in gaskets and rope packing on flanges and doors, in friction materials on cranes and hoists, and in old electrical equipment such as arc chutes and switchgear panels. Ships built before the 1990s often contain large amounts of insulation, deck coverings, gaskets and fire barriers. Rail cars, locomotives, buses and older heavy equipment may have asbestos in brakes, clutches, gaskets and insulation.

Maintenance on this equipment is often done by mechanics, millwrights, boilermakers and electricians who may not think of themselves as working with asbestos. Plants with older equipment should include equipment, not only buildings, in their asbestos inventory, label known asbestos components, and include asbestos checks in work permits and maintenance planning, so that a gasket change or a furnace repair is done with the right controls.