The Heat & Frost Insulators craft formed in the late 19th and early 20th centuries as American industry built out its first generation of pressurized steam systems. The trade grew alongside the construction of central heating plants, electric utility generating stations, oceangoing ships, refineries, and the network of pipe-distribution systems that connected them. Insulators were the trade that put the heavy thermal coatings on the heated equipment that made all this work possible.

The asbestos era

From roughly 1920 through the late 1970s, the standard materials of the Heat & Frost Insulators trade were asbestos-containing. The reasons were industrial — asbestos was cheap, abundant, fireproof, easy to apply, mechanically durable, and chemically stable at the high temperatures that 20th-century industry required. The reasons were also commercial — the suppliers of asbestos pipe covering, block insulation, refractory products, gaskets, and cement built a marketing infrastructure around the insulator trade that ensured these were the products specified on virtually every industrial construction project for half a century.

The trade did not choose this. Members were dispatched to jobsites where these materials were specified by architects, engineers, and construction managers. They installed, removed, and reinstalled them according to the specifications and timelines of their contractors. They worked in the conditions that the construction sites provided — sometimes with ventilation, often without; sometimes with respiratory protection, more often not.

The Mount Sinai studies and federal recognition

In the 1960s and 1970s, federal occupational-health research — most prominently the work of Dr. Irving Selikoff and his colleagues at Mount Sinai Hospital in New York — documented the scale of the asbestos health crisis among insulators. The Mount Sinai studies, drawing their cohort heavily from Local 1 members in the New York metropolitan area, established that the rate of mesothelioma and other asbestos-related cancers among career insulators was an order of magnitude above the general-population baseline.

These findings led to OSHA’s first asbestos exposure regulations in 1971 and to a decades-long process of removing asbestos products from the trade’s standard materials. By the late 1980s, calcium silicate, fiberglass, mineral wool, ceramic-fiber, and engineered foam systems had replaced most asbestos-bearing materials in new construction. But the disease pipeline — driven by the 20 to 50 year latency between exposure and diagnosis — continued, and continues today, for workers whose careers fell within the asbestos era.

What the trade did

Through the asbestos era, Heat & Frost Insulators were dispatched to four broad categories of work:

  1. New construction — applying thermal insulation to new boilers, pipe runs, ducts, and equipment in newly built power plants, factories, ships, hospitals, and institutional buildings
  2. Maintenance and outage work — periodic re-insulation of existing equipment during planned shutdowns
  3. Repair and rip-out — removing damaged or end-of-life insulation, often in the highest-fiber-release conditions of the trade
  4. Specialty work — refractory in furnaces and boilers, fireproofing on structural steel, asbestos cloth jacketing on bare piping

Each category had its own characteristic exposure profile. Rip-out work — particularly during plant turnarounds at refineries, steel mills, and power plants — produced the highest concentrations of airborne fiber. New construction was lower-intensity but longer-duration. Specialty work like refractory tear-out at coke ovens, blast furnaces, and recovery boilers concentrated members in unventilated indoor spaces for the duration of an outage.

Allied trades

The Heat & Frost Insulators worked alongside several allied crafts that share parts of the asbestos exposure history:

  • Pipefitters / Steamfitters — fitting the pipe that insulators then covered
  • Boilermakers — fabricating and repairing the boilers and pressure vessels insulators worked around
  • Sheet Metal Workers — fabricating the jacketing that finished insulator work
  • Millwrights — installing the mechanical equipment that insulators covered
  • Refractory Bricklayers — laying the high-temperature furnace and boiler linings

All five trades have documented mesothelioma rates well above the general population. The Heat & Frost Insulators are typically at the top of the list because their daily handling of the asbestos materials themselves was the most direct.

Today

The trade today has largely transitioned to non-asbestos materials. Members who entered the apprenticeship in the late 1980s or later worked through a substantially safer materials regime. But the disease tail of the asbestos era continues. Insulators who entered the trade in the 1950s, 1960s, and 1970s — now in their 60s, 70s, and 80s — are the population now being diagnosed with mesothelioma and other asbestos-related diseases at the highest rates.

This site exists to document that history and, where applicable, to help affected members and families navigate the claims process under the asbestos bankruptcy trusts and state-specific litigation frameworks that compensate workers and survivors of asbestos exposure.

See Asbestos Products → · See Workplaces → · See Local Unions →