Asbestos insulation: pipe covering, block, and insulating cement

Asbestos insulation wrapped the pipes, boilers, and turbines of American industry for most of the twentieth century, and the danger came from the everyday work of cutting it to fit and tearing the old, crumbling lagging (the insulation wrapped around a pipe) back out. Hand-sawing a length of amosite pipe covering has been measured at 51.7 fibers per cubic centimeter, which in fifteen minutes puts roughly fifteen years' worth of ordinary city background air through a worker's lungs¹, and the companies that made this material had been studying the disease it caused for decades before the last of it left the market. You don't need to remember which brand you cut or dig up any old records to find out whether you have a claim; if you worked around this material, that's where we start.

Even ordinary city air carries a faint trace of asbestos everywhere, from natural mineral erosion and decades of industrial use, and that trace is the baseline both sides of the panel are measured against.

What these numbers mean. Asbestos in air is measured in fibers per cubic centimeter (f/cc), a unit that hides how dangerous a task was. Across this site we translate each measurement into fibers breathed, feet of fiber end to end, and years of ordinary city air, using conservative, government-sourced assumptions. See how we measure asbestos in air for the method and its limits.

What asbestos insulation was

Thermal insulation is the material that kept heat where it belonged: wrapped around steam pipes, packed against boiler walls, molded over turbine casings, and troweled into the gaps in between. For most of the twentieth century the best insulation for the job was made of asbestos, because asbestos held its shape and its insulating value against heat and vibration that would break down anything else. Wherever a system ran hot, the covering on it was very likely asbestos.

It came in a handful of standard forms, and the exposure hazard was built into how each one was handled. Sectional pipe covering was rigid half-round shells, sized to a pipe's diameter, that a worker cut to length and snapped around the pipe. Block insulation was flat or curved slabs used on boilers, tanks, and large flat surfaces, cut and shaped to fit with a saw. Insulating cement was a dry asbestos powder mixed with water into a paste and troweled over fittings, elbows, and valves that the rigid forms couldn't cover, and the mixing of that dry powder was its own dusty job. Spray fireproofing was asbestos slurry sprayed onto steel beams and decks; it has its own hazards and its own page.

Spray fireproofing sat at the extreme end of the insulation category and carried some of the highest measured fiber levels of any asbestos work; we cover it on its own page rather than here, because the numbers and the products differ enough to deserve their own treatment. See spray-applied asbestos fireproofing.

Play the film from 13:48: Heat: The Science and Economics of Its Control from 13:48

Representative products and their asbestos content. These are examples, not a full list:

How asbestos insulation put asbestos in the air

Insulation released fiber at every stage a worker touched it. Sizing rigid pipe covering meant hand-sawing the shells to length, and the saw threw dry fiber straight into the breathing zone. Fitting block meant cutting and beveling slabs to shape. Insulating cement had to be mixed from a dry powder, and pouring and stirring that powder raised a cloud before a drop of water went in. And the dirtiest job of all came at the far end of the product's life: tearing out old, degraded lagging during a repair or a demolition, when insulation that had baked and crumbled for decades came off in friable (crumbly and dusty) chunks that filled the air.

Here is what that work measured. Each figure is a phase-contrast (PCM) measurement, which counts only the longer fibers and so it's a minimum exposure measurement.

By the illustrative math on our how we measure asbestos in air page, 15 minutes of hand-sawing amosite pipe covering put roughly 15 years of ordinary city air through the lungs. This estimates fibers in the air breathed, not a retained dose.

What the makers knew

Insulation is the product category where the corporate-knowledge record is oldest and deepest, because the disease that insulation caused was documented in the workers who installed it, by name, decades before the last of the product left the market.

The foundational epidemiology was about these workers doing exactly this work. Beginning with Selikoff, Churg, and Hammond in 1964, Irving Selikoff's Mount Sinai studies followed a large cohort of insulation workers and established the link between insulation work and both asbestosis and mesothelioma in the medical literature⁴. This wasn't a general finding about asbestos that happened to touch insulation; the mortality studies that put mesothelioma on the map were studies of insulators.

The manufacturers' own knowledge ran back further still. The Sumner Simpson papers, a cache of correspondence beginning in 1935, document that Johns-Manville and others in the industry knew of the asbestos-disease hazard from the mid-1930s and chose not to warn the workforce⁵. A company that has been reading its own hazard correspondence since 1935 and is still selling 98% chrysotile pipe covering decades later is not a company that can claim it didn't know.

The Kaylo record carries the same theme through a change of ownership. Owens-Illinois introduced Kaylo pipe covering and block in 1948 and sold the line to Owens-Corning in 1958, which kept making it into the 1970s. Both companies carried the knowledge forward with the product, which is why a Kaylo claim can reach either one depending on when the exposure happened. Learn more about Kaylo.

And the science kept sharpening the point about fiber type. Later work put amphibole asbestos at roughly two to four times the potency of chrysotile for mesothelioma⁶, which matters directly here because so much insulation, from Unibestos and Kaylo pipe covering to amosite-bearing block, was amphibole.

Who was exposed

Insulation wasn't tied to one trade or one place; it was on every hot line and every boiler, and the crews that installed it worked shoulder to shoulder with everyone else in the space. Rather than retell each worker's story here, this page hands that off to the pages that own it:

• insulators and insulation workers, the primary trade, who cut and installed this material every day
• pipefitters and plumbers, who worked the same lines the insulation covered
• boilermakers on the boilers and their block insulation
• shipyards and the Navy, where engine and boiler rooms were packed with insulated steam systems
• power plants and refineries, where miles of hot piping ran on asbestos covering

If you or your family member worked around insulated piping or boilers in any of these settings, the exposure history is usually easy to reconstruct.

The manufacturers and the trusts

Insulation is, more than almost any other product category, a trust-claim category. Nearly every major maker of pipe covering, block, and insulating cement went bankrupt under the weight of asbestos litigation, and each set up a court-supervised trust to pay claims. That's good news for families: a trust claim is a paper process that doesn't require a lawsuit against a company that no longer exists. The main solvent avenue that remains is premises liability against the site owners whose plants, ships, and utilities were full of this material.

One split on this table is worth calling out because it's a real, actionable detail: which trust a Kaylo claim routes to depends on the exposure dates. Exposure to Kaylo before Owens-Illinois sold the line in 1958 points toward the Owens-Illinois trust; exposure after 1958 points toward Owens-Corning. Getting the dates right is part of building the file. Any question of whether a claim reaches a particular successor company is a legal analysis we work through for you rather than something you need to sort out.

Sources of compensation

An insulation case usually draws from more than one source, and they run in parallel rather than competing:

• Asbestos bankruptcy trusts. The makers who went bankrupt set aside money to pay the people they harmed. These are paper claims, with no lawsuit and no courtroom, and one career around insulation often supports filings against several trusts at once. How asbestos trust claims work.
• Product-liability lawsuits. Where a solvent maker or successor remains in the picture, a direct lawsuit can be part of the case. How product liability lawsuits work.
• Premises liability against site owners. The refineries, utilities, shipyards, and plants that controlled the worksite can be held responsible for the insulated conditions they allowed. How premises liability claims work.
• Federal and disability benefits. Navy service can support VA disability benefits, and civilian shipyard work can support Longshore (Longshore and Harbor Workers' Compensation Act) benefits, both paid in addition to the rest. How asbestos disability and benefit claims work.

The makers and premises defendants raise the same handful of arguments in most insulation cases, and none is new to us. All of this applies only to the lawsuit side. Trust claims are a paper process: no opposing lawyer raises defenses, no one is deposed, and no one goes to court.