Kaowool Ceramic Fiber Products (Post-Asbestos Transition) — Harbison-Walker

Product Description

Kaowool is a brand of ceramic fiber insulation products manufactured by Harbison-Walker Refractories, one of the leading refractory materials companies in the United States for much of the twentieth century. Ceramic fiber products under the Kaowool name were developed and marketed primarily as high-temperature insulation solutions for industrial furnaces, kilns, boilers, and other thermal processing equipment. The product line was positioned as a successor generation of refractory insulation, designed to replace earlier materials — including those that contained asbestos — in applications requiring resistance to extreme heat.

Kaowool products were manufactured in a variety of forms, including blankets, boards, modules, and bulk fiber, all intended for use in settings where conventional insulation materials could not withstand operating temperatures. These products were widely adopted across industries such as steel production, aluminum processing, glass manufacturing, ceramics, petrochemical refining, and power generation. Harbison-Walker marketed Kaowool extensively to plant operators and industrial contractors as a modern, high-performance refractory solution suited to demanding continuous-process environments.

Despite being characterized as a post-asbestos product line, Kaowool ceramic fiber materials have been the subject of significant occupational health concern and subsequent litigation and trust fund claims related to the broader history of Harbison-Walker’s operations and product portfolio.

Asbestos Content

Kaowool ceramic fiber products in their post-transition formulations were not manufactured with intentionally added asbestos. The fibers used in Kaowool blankets, boards, and bulk materials are refractory ceramic fibers (RCFs) — primarily composed of alumina and silica — rather than asbestiform minerals. This distinction is important to the product’s marketing history: Harbison-Walker promoted Kaowool and similar ceramic fiber lines in part as alternatives to asbestos-containing refractory products.

However, the legal and health significance of Kaowool within the context of Harbison-Walker’s liability history arises from several factors. First, Harbison-Walker manufactured and sold a broad range of asbestos-containing refractory products throughout the twentieth century, and workers who handled or installed Kaowool products often worked alongside, or in facilities contaminated by, legacy asbestos-containing Harbison-Walker materials. Cross-contamination and co-exposure in industrial environments were documented concerns in occupational health records and litigation proceedings.

Second, refractory ceramic fibers themselves have been classified by the International Agency for Research on Cancer (IARC) as possibly carcinogenic to humans (Group 2B), and certain high-temperature variants have been reclassified to Group 2A (probably carcinogenic). OSHA has established permissible exposure limits for RCFs, and the agency has required hazard communication, engineering controls, and medical surveillance for workers exposed to ceramic fiber products. These regulatory actions reflect the recognized respiratory hazard profile of ceramic fiber insulation independent of asbestos content.

Third, claims filed with the Harbison-Walker International Asbestos PI Trust may encompass exposures tied to Kaowool in the context of broader Harbison-Walker product exposure histories, particularly when workers were exposed to multiple product lines from the same manufacturer across their careers.

How Workers Were Exposed

Industrial workers in a wide range of trades and facilities encountered Kaowool ceramic fiber products during installation, maintenance, repair, and demolition of high-temperature industrial equipment. The following work scenarios have been documented in occupational health literature and litigation records as creating conditions for fiber release and inhalation:

Installation and fabrication. Workers cutting, tearing, or fitting Kaowool blankets and boards to line furnaces, kilns, and boilers generated airborne ceramic fibers. Cutting operations using knives, saws, or manual tearing released respirable fiber concentrations into work area air. Workers performing these tasks in enclosed or poorly ventilated spaces faced elevated exposure levels.

Furnace repair and relining. Industrial maintenance personnel tasked with relining or repairing high-temperature equipment removed degraded ceramic fiber modules and blankets, generating significant dust. Older fiber materials that had been subjected to repeated thermal cycling were often more friable and prone to releasing airborne particles during disturbance.

Maintenance and adjacent trades. Pipefitters, boilermakers, millwrights, and other skilled trades workers who performed work near furnaces and kilns lined with Kaowool materials were exposed to fibers disturbed by others’ work, even when they were not directly handling the product themselves. Bystander exposure in industrial plant environments was a recognized pattern.

Demolition and changeout operations. Full furnace demolitions and scheduled equipment changeouts required the removal and disposal of large quantities of ceramic fiber lining materials. Workers performing this work, as well as those working in the same facility, faced concentrated exposures during these operations.

Industrial workers generally — including those employed at steel mills, foundries, glass plants, aluminum smelters, refineries, and manufacturing facilities — represent the population most directly exposed to Kaowool products over the decades of the product line’s commercial availability.

Harbison-Walker’s own product literature and safety data communications evolved over time in response to regulatory developments, but occupational health advocates and litigants have documented that hazard information was not always provided to workers in a timely or actionable manner.