CM Gun Mix / CM-18 Gun Mix — NARCO Refractory Product

Manufacturer: North American Refractories Company (NARCO) Product Line: CM Gun Mix / CM-18 Gun Mix Category: Refractory Gunning Mix Production Period: 1963–1977

Product Description

CM Gun Mix and CM-18 Gun Mix were pneumatically applied refractory gunning materials manufactured by North American Refractories Company, widely known in industrial circles as NARCO. NARCO was one of the leading producers of refractory products in the United States throughout much of the twentieth century, supplying materials to steel mills, foundries, glass plants, cement kilns, and other high-temperature industrial operations.

Refractory gunning mixes were specialized materials engineered to withstand extreme heat. Unlike brick-formed refractory linings installed by hand, gunning mixes were designed to be applied through pneumatic spray equipment — a process commonly referred to as “gunning” or “shotcreting.” This method allowed workers to apply refractory coatings rapidly to the interior surfaces of furnaces, ladles, boilers, kilns, and other industrial vessels, including during repair and maintenance operations that could not wait for extended equipment shutdowns.

CM Gun Mix and its CM-18 variant were marketed specifically for their high-temperature performance characteristics, making them commercially attractive to industries that demanded durable lining materials capable of surviving repeated thermal cycling. NARCO distributed these products widely across American industrial sectors during the 1963–1977 production window, meaning they appeared in workplaces throughout the country during decades when occupational asbestos exposure regulations were minimal or unenforced.

Asbestos Content

CM Gun Mix and CM-18 Gun Mix contained asbestos as a component of their refractory formulation. Asbestos was incorporated into refractory gunning mixes during this era for several functional reasons. Its fiber structure contributed to the cohesion and workability of the sprayed material, helped bind the mix to vertical and overhead surfaces during application, and enhanced the thermal stability of the cured lining. Asbestos fibers also improved the overall tensile characteristics of the hardened refractory mass, reducing cracking under the mechanical and thermal stresses common inside industrial furnaces and vessels.

The use of asbestos in refractory gunning compounds was an industry-wide practice during the mid-twentieth century. NARCO, as a major commercial supplier, formulated CM Gun Mix and CM-18 Gun Mix in line with industry standards of the time. The presence of asbestos in these products has been confirmed through trust fund documentation associated with NARCO’s asbestos liability history and is reflected in the establishment of the North American Refractories Company Asbestos PI Trust.

How Workers Were Exposed

The method of applying CM Gun Mix and CM-18 Gun Mix created conditions that were particularly hazardous from an inhalation standpoint. Pneumatic gunning — the process these products were engineered for — involves forcing the dry or semi-dry refractory mix through a hose under compressed air and projecting it at high velocity onto a surface. This process inherently generates significant airborne dust, and when that mix contained asbestos fibers, the dust carried respirable asbestos into the breathing zone of workers in the immediate area and throughout the surrounding workspace.

Industrial workers directly operating gunning equipment faced sustained, high-concentration exposure during application. Workers managing hose lines, nozzle positions, or material feed also encountered elevated fiber levels. Equally at risk were nearby trades workers — those performing concurrent maintenance, inspection, or construction tasks in the same industrial space — who inhaled asbestos-laden dust without necessarily having any direct contact with the gunning mix itself.

Beyond initial application, CM Gun Mix and CM-18 Gun Mix created secondary exposure opportunities throughout their service life. When refractory linings containing asbestos were removed, chipped, broken out, or otherwise disturbed during maintenance shutdowns or vessel relining operations, the previously hardened material could release asbestos fibers. Workers involved in demolishing old refractory linings — often with pneumatic hammers or hand tools — faced intense short-duration exposures during these tear-out operations.

Documented exposure pathways associated with NARCO’s CM Gun Mix products include:

  • Mixing and preparation of the gunning compound prior to application
  • Pneumatic spray application inside furnaces, ladles, converters, and kilns
  • Bystander exposure in shared industrial workspaces during gunning operations
  • Refractory demolition and relining activities where cured CM Gun Mix material was broken out
  • Equipment cleaning and maintenance involving gunning machinery and associated hardware

Workers in steel production, foundry operations, cement manufacturing, glass production, and petrochemical processing were among those most likely to have encountered CM Gun Mix or CM-18 Gun Mix during normal industrial operations between 1963 and 1977. The industrial settings where these products were used typically involved enclosed or semi-enclosed spaces with limited ventilation, conditions that allowed airborne fiber concentrations to reach and remain at dangerous levels during work activities.

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.