Keene Monospray / Pyrospray / Thermasil Spray Fireproofing

Keene Corporation manufactured a line of spray-applied fireproofing products—sold under the trade names Monospray, Pyrospray, and Thermasil—that contained chrysotile asbestos as a primary ingredient. Produced and distributed between approximately 1962 and 1973, these materials were applied to structural steel and other building components across commercial, industrial, and institutional construction projects throughout the United States. Workers who mixed, applied, or worked in proximity to these spray fireproofing products during their active use—and in some cases during later renovation or demolition activities—faced documented exposure to airborne asbestos fibers.

Product Description

Keene Corporation’s Monospray, Pyrospray, and Thermasil products belonged to a category of construction materials known as spray-applied fire-resistive materials (SFRMs). These products were designed to meet building code requirements for passive fire protection, particularly on structural steel beams, columns, decking, and other load-bearing components. When heated steel loses structural integrity rapidly, spray fireproofing was intended to insulate the steel and slow that process, buying time for building evacuation and fire suppression.

During the period of manufacture—roughly 1962 through 1973—the SFPM industry broadly relied on asbestos fibers to provide heat resistance, binding strength, and adhesion to metal surfaces. Keene’s product line, marketed under three distinct trade names, was part of this wider industry practice. The products were sold in dry form and mixed with water on-site before being sprayed onto surfaces using pneumatic equipment. Once cured, the material formed a lightweight, fibrous coating that remained in place as long as the building stood undisturbed.

These products were applied in a wide range of building types, including office towers, schools, hospitals, industrial facilities, and public infrastructure projects constructed or renovated during the 1960s and early 1970s. Buildings constructed during this era that have not undergone abatement may still contain Keene fireproofing materials in place.

Asbestos Content

Keene Monospray, Pyrospray, and Thermasil contained chrysotile asbestos, the most commonly used form of asbestos in commercial building products during the mid-twentieth century. Chrysotile, also called white asbestos, was valued in fireproofing applications for its fibrous tensile strength, heat resistance, and ability to bond with binding agents and mineral compounds.

In spray fireproofing products of this era, asbestos fibers were typically present in significant concentrations by weight, functioning as the primary structural and insulating component of the finished material. The U.S. Environmental Protection Agency’s Asbestos Hazard Emergency Response Act (AHERA) framework, along with OSHA asbestos standards codified under 29 C.F.R. § 1926.1101 and § 1910.1001, recognize spray-applied asbestos fireproofing as a high-priority category of asbestos-containing material (ACM) due to its friable nature. Friable materials can be reduced to powder by hand pressure, releasing respirable fibers into the air during disturbance.

Asbestos fibers in the chrysotile category are classified as known human carcinogens by the International Agency for Research on Cancer (IARC), the National Toxicology Program, and regulatory bodies in the United States and internationally. Inhalation of respirable chrysotile fibers is associated with asbestosis (progressive pulmonary fibrosis), lung cancer, and mesothelioma, a malignancy of the pleural or peritoneal lining.

How Workers Were Exposed

Litigation records document that workers across multiple trades and industrial settings encountered Keene Monospray, Pyrospray, and Thermasil during their production, mixing, application, and finishing phases. Because these products were spray-applied, the application process was among the most hazardous points of exposure: pneumatic spray equipment dispersed fine fibers into the air throughout the immediate work area and into adjacent zones of the construction site.

Mixing and loading operations required workers to open bags of dry product, pour the contents into hoppers or mixing vessels, and combine the material with water. This process generated visible dust clouds containing asbestos fibers. Workers performing these tasks often did so without respiratory protection, as widespread enforcement of asbestos exposure limits was not yet in place during the early years of these products’ use.

Application workers—those operating spray equipment directly—worked in the closest proximity to aerosolized material and faced some of the highest concentrations of airborne fiber during active spraying. Plaintiffs alleged in litigation that Keene Corporation was aware of the hazards associated with airborne asbestos during the period of manufacture yet did not adequately warn workers about the risks or provide guidance on protective measures.

Finishing and cleanup workers who trimmed overspray, swept debris, or otherwise disturbed cured or partially cured fireproofing material also faced significant exposure. Spray fireproofing that had not fully bonded, or that had been disturbed by subsequent construction activities, could release fibers during handling.

Bystander exposure was also documented in litigation records. Workers in trades such as ironworking, electrical, plumbing, and general construction who worked in the same building areas where Monospray, Pyrospray, or Thermasil was being applied—or where previously applied material was being disturbed—could inhale fibers without directly handling the product themselves.

Beyond initial construction, building maintenance workers, renovation contractors, and demolition crews working in structures where Keene fireproofing remained in place have also alleged exposure in subsequent decades. Disturbing intact asbestos-containing spray fireproofing during renovation or demolition activities can release fibers at levels well above occupational exposure limits set by OSHA.

Documented Product Identification

The following details are drawn from public asbestos litigation records, manufacturer catalog pages, technical manuals, and corporate history materials. Each item reflects the product as documented in those sources.

Documented asbestos-use period: 1971-1972

Corporate context: Ehret Magnesia Manufacturing Company was acquired by Keene Corporation. Keene produced industrial and commercial insulation products containing asbestos.

Brand identification: KEENE, Ehret, FibreKote, Thermasil, Mono-Block, Mono-Spray, Super Powerhouse, No. 1 Plus

Documented asbestos components: pipe covering, asbestos felt, asbestos fibres, insulation, asbestos fiber.

Industries served: commercial construction, building industry, industrial insulation, military, US Coast Guard.

Naval / marine service: This manufacturer’s equipment is documented in connection with U.S. Navy and commercial-marine service.

Documented product lines:

  • Ehret 85% Magnesia Pipe Covering. 85% magnesia-based thermal pipe covering insulation. — asbestos components: pipe covering.
  • KEENE 8 oz Canvas Jackets 45# (1971-1972). Asphalt saturated asbestos felt jackets used for pipe and vessel insulation, compliant with Federal, Military, US Coast Guard and ASTM standards. — asbestos components: asbestos felt.
  • FibreKote (1971-1972). Coating/finishing material containing long asbestos fibres used in installation and construction of piping, vessels, and various insulation products. — asbestos components: asbestos fibres.
  • Thermasil Pipe and Block Insulation (1971-1972). Pipe and block thermal insulation installed with FibreKote asbestos-containing material. — asbestos components: insulation.
  • Metal Mesh Blanket Insulation (1971-1972). Blanket-style insulation used with FibreKote asbestos-containing finishing compound. — asbestos components: insulation.
  • Mono-Block Mineral Fiber Block Insulation (1971-1972). Mineral fiber block insulation product used with asbestos-containing FibreKote. — asbestos components: insulation.
  • Spun Felt Mineral Fiber Felt Insulation (1971-1972). Mineral fiber felt insulation applied with FibreKote. — asbestos components: insulation.
  • Mono-Spray, Spun and Monolithic Thermal Insulation (1971-1972). Spray-applied and monolithic thermal insulation products. — asbestos components: insulation.

Keene insulation products were documented as Federal, Military, and US Coast Guard compliant. FibreKote asbestos-containing finishing compound was used across multiple insulation product lines for pipe, vessel, and building applications.