Asbestos Millboard — Asbestos Exposure Crosswalk

What This Equipment Is

Asbestos millboard is a rigid pressed sheet made by combining chrysotile asbestos fiber with a small fraction of inorganic or organic binder and pressing the wet pulp into uniform sheets — typically 1/8 to 1/2 inch thick. The product looks superficially like a dense fiberboard but is fully mineral. It is dimensionally stable to roughly 1,200°F and was the workhorse high-temperature gasket and shielding material for most of the twentieth century.

Common uses included:

  • High-temperature gasketing — flange seals where conventional sheet gasket would fail
  • Furnace and boiler backer — sheet placed behind brick or castable as a back-up layer
  • Burner-port shielding — heat shields around burner penetrations
  • Electrical insulation — high-voltage barriers, arc-chute components, switchgear barriers
  • Fume-hood and laboratory bench backers — non-combustible work-surface backing
  • Foundry tooling — pour-trough liners and ladle covers
  • Removable insulation blanket interiors — the rigid component inside sewn insulation jackets

Why Millboard Work Was a High-Exposure Activity

Millboard is friable — it can be cut, scribed, and snapped to fit by hand. Cutting, drilling, and scribing released chrysotile fiber freely. Workers fabricated custom millboard pieces on the job for gaskets, shields, and backers, generating fiber at close range.

In service, intact millboard is relatively stable. Exposure during maintenance and demolition comes when the material is broken out — replacing aged gaskets, removing furnace back-up layers during a reline, tearing down old electrical switchgear, or demolishing fume hoods and lab benches.

Manufacturers Named in Asbestos Millboard Litigation

  • Johns-Manville — millboard product line (Transite-grade and similar)
  • Armstrong World Industries — millboard products
  • Raybestos-Manhattan — millboard products
  • H.K. Porter / Southern Asbestos — millboard
  • Asbestospray Corporation — millboard
  • Carey-Canada / Philip Carey Manufacturing — millboard

Documented Product References

Images sourced from publicly available product-identification reference materials. Inclusion does not constitute a finding of liability against any company.

Trust Funds That May Apply

  • Manville Personal Injury Settlement Trust
  • Armstrong World Industries Asbestos PI Settlement Trust
  • Raybestos-Manhattan Asbestos PI Trust
  • H.K. Porter related trusts

Trades Most Exposed at Asbestos Millboard Work

Insulators (Heat & Frost), refractory masons handling back-up layers, electricians fabricating switchgear barriers, sheet-metal mechanics on furnace and combustion equipment, laboratory and casework installers, foundry pattern shop workers, building demolition and renovation crews.

Jobsites in the Network Documenting Asbestos Millboard

Compiled from publicly filed asbestos litigation, EPA / state-DNR records, and industry-publication histories. Product and company references reflect what has been alleged or documented in publicly filed litigation. This page does not constitute a finding of liability against any company. Not legal advice; consult a licensed attorney about your specific situation.