Narcogun CM-343 / CR-346 / MCD-344 / P-340 / MC-339

Manufacturer: North American Refractories Company (NARCO) Product Category: Gunning Refractory Mix Years Produced: 1964–1977 Asbestos Type: Chrysotile

Product Description

Narcogun was a line of pneumatically applied gunning refractory materials manufactured by North American Refractories Company (NARCO) between 1964 and 1977. The product line included several distinct formulations designated CM-343, CR-346, MCD-344, P-340, and MC-339, each engineered for specific high-temperature industrial applications. These mixes were designed to be installed using compressed-air gunning equipment, which propelled the refractory material at high velocity onto furnace linings, ladles, kilns, boilers, and other heat-processing vessels that required durable thermal protection.

NARCO was a major supplier of refractory products to heavy industry throughout the mid-twentieth century, serving steel mills, aluminum smelters, glass plants, and other facilities that operated large-scale furnaces and heat-processing equipment. The Narcogun product line was widely used across these industries because gunning refractory application offered a faster, less labor-intensive alternative to hand-laid refractory brick for lining repairs and new installations. Workers could apply or patch furnace linings while equipment was in service or during brief shutdowns, making Narcogun products operationally valuable to facilities running continuous production operations.

The five formulations in the Narcogun line were differentiated by their intended service temperatures, chemical compositions, and target substrates. Some variants were formulated for ferrous applications such as electric arc and basic oxygen furnaces used in steelmaking, while others were suited to non-ferrous processing environments, including aluminum reduction and holding furnaces. Despite their varying end uses, all five formulations shared a common manufacturing characteristic: the use of chrysotile asbestos as a binding component within the refractory mix.

Asbestos Content

Each formulation in the Narcogun product line — CM-343, CR-346, MCD-344, P-340, and MC-339 — incorporated chrysotile asbestos as a functional binder within the gunning refractory mix. Chrysotile, the most commercially used form of asbestos, was selected by refractory manufacturers during this period for its heat resistance, tensile strength, and ability to hold granular refractory aggregates together during and after application.

In gunning refractory products, asbestos binders served a structural role: they helped the sprayed material adhere to vertical and overhead surfaces, reduced rebound loss during pneumatic application, and contributed to the mechanical integrity of the cured lining. These performance characteristics made asbestos-containing binders common across the refractory gunning industry during the decades when the Narcogun products were produced.

NARCO manufactured the Narcogun line from 1964 through 1977, a period during which asbestos content in refractory products was standard industry practice and largely unregulated. The U.S. Environmental Protection Agency’s Asbestos Hazard Emergency Response Act (AHERA) and OSHA’s asbestos standards, developed in subsequent years, later established the regulatory framework that identified chrysotile-containing products as sources of occupational disease risk.

How Workers Were Exposed

Workers who handled, mixed, applied, or worked in proximity to Narcogun CM-343, CR-346, MCD-344, P-340, and MC-339 faced the potential for significant asbestos fiber exposure through several mechanisms inherent to the product’s use.

Refractory Workers (Brickies and Gunners): Refractory installers and gunners were the most directly exposed trade. During pneumatic application, the gunning process generated clouds of airborne dust as the dry mix was propelled through the gun and struck the target surface. Rebound material — the portion of the mix that did not adhere — fell to the work area floor, creating secondary dust when disturbed. Workers who prepared and loaded the dry gunning mix into hoppers also handled the asbestos-containing material directly, often in enclosed or poorly ventilated furnace interiors.

Steel Mill Furnace Workers: Steelworkers, including furnace operators and maintenance personnel, were exposed when Narcogun products were applied to or repaired within electric arc furnaces, basic oxygen furnaces, ladles, and other steelmaking vessels. Exposure could occur during application operations, during shutdown periods when furnace linings were inspected or repaired, and when deteriorating refractory linings shed fibrous material into the work environment.

Boilermakers: Boilermakers who installed and maintained industrial boilers lined with gunning refractory materials encountered Narcogun products in utility plants, industrial facilities, and marine applications. Installation, patching, and removal of refractory linings in boiler fireboxes and combustion chambers placed boilermakers in close contact with airborne dust generated by both application and mechanical disturbance of cured material.

Aluminum Plant Workers: Workers at aluminum smelters and processing facilities were exposed when Narcogun formulations were used to line or repair holding furnaces, reduction cells, and transfer equipment. Aluminum production environments often required frequent lining repairs due to the corrosive nature of molten aluminum and the thermal cycling these vessels underwent, leading to repeated and sustained worker exposure over the course of individual careers.

Across all trades, a significant proportion of exposure occurred in confined or enclosed spaces — furnace interiors, boiler fireboxes, and industrial vessels — where natural ventilation was minimal and airborne fiber concentrations could reach elevated levels. Workers in adjacent areas who were not directly applying the product but were present during gunning operations faced bystander exposure under these conditions.

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.

Corporate context: Formed in 1929 through the merger of several refractory companies including Queen’s Run, Crescent, and Eltra, among others. Owned by Eltra until 1979, then by Allied Signal (Allied) from 1979 to 1986, after which ownership transferred to banks and investors. Headquartered in Cleveland, Ohio.

Brand identification: Narco

Industries served: steel, iron.

North American Refractories Company (Narco) manufactured refractory materials used primarily in high-temperature industrial applications such as steel and iron processing. The company operated approximately eleven manufacturing facilities and a research center in Curwensville, Pennsylvania.