WO-339 MC Gun — Asbestos-Containing Pipe Insulation Product

Manufacturer: Narco
Product Category: Pipe Insulation
Years Produced: 1964–1975
Asbestos Type: Chrysotile
Legal Status: Tier 2 — Litigated Product

Product Description

The WO-339 MC Gun was an industrial pipe insulation product manufactured by Narco during the period spanning 1964 through 1975. Products of this type were developed to meet the thermal insulation demands of industrial facilities, where high-temperature pipe systems required durable, heat-resistant coverings capable of withstanding sustained operational stress. Pipe insulation materials in this class were widely deployed across refineries, power generation plants, manufacturing facilities, chemical processing plants, and other heavy industrial environments where piping networks carried steam, hot fluids, or process chemicals at elevated temperatures.

During the production era of the WO-339 MC Gun, asbestos-containing materials were the dominant choice for thermal insulation applications across industrial sectors. Asbestos was valued by manufacturers for its resistance to heat, fire, and chemical degradation, as well as its structural binding properties when incorporated into insulation compounds. Narco, as a manufacturer serving industrial markets, produced the WO-339 MC Gun during a period when regulatory standards governing asbestos use in occupational settings had not yet been fully established or enforced.

The product name references a “gun” application method, indicating that the insulation compound was designed to be applied using spray or pump equipment — a delivery mechanism common to pipe-coating and lagging applications of this era. This application format was widely used in industrial construction and maintenance settings throughout the 1960s and early 1970s.

Asbestos Content

The WO-339 MC Gun contained chrysotile asbestos as a component of its insulation formulation. Chrysotile, also referred to as white asbestos, is the most commercially prevalent form of asbestos and belongs to the serpentine mineral group. Its fibrous, flexible structure made it well suited for integration into insulation compounds, where it contributed to the thermal resistance, tensile strength, and fire-retardant properties of the finished product.

Although chrysotile fibers have a different physical structure than amphibole asbestos varieties such as amosite or crocidolite, regulatory and scientific bodies including the U.S. Environmental Protection Agency (EPA) and the Occupational Safety and Health Administration (OSHA) have classified all forms of asbestos, including chrysotile, as known human carcinogens. OSHA’s asbestos standards, codified in 29 C.F.R. § 1910.1001 (general industry) and 29 C.F.R. § 1926.1101 (construction), establish permissible exposure limits and specify handling requirements applicable to chrysotile-containing materials.

Under the Asbestos Hazard Emergency Response Act (AHERA) framework, products containing one percent or more asbestos by weight are subject to regulatory requirements governing identification, management, and abatement. Pipe insulation products from this production era routinely met or exceeded that threshold.

How Workers Were Exposed

Industrial workers who handled, applied, or worked in proximity to the WO-339 MC Gun faced potential asbestos fiber exposure through several pathways inherent to the product’s intended use and application method.

The gun-application format used for this product type involved loading asbestos-containing insulation compound into spray or pump equipment and directing the material onto pipe surfaces under pressure. This process was known to generate airborne particulate, including respirable asbestos fibers, in the immediate work area. Workers operating the application equipment, as well as those nearby during the application process, could inhale fibers released into the surrounding environment.

Once applied, pipe insulation of this type required finishing, trimming, and surface work that involved cutting, sanding, or abrading the cured material. These secondary operations are recognized mechanisms for fiber release. Additionally, aging or damaged insulation on in-service pipe systems could deteriorate over time, releasing fibers during routine maintenance, repair, or inspection activities. Workers assigned to perform maintenance on insulated piping — or to remove and replace existing insulation — faced ongoing exposure risk throughout the operational life of the installed material.

Industrial workers generally, including pipefitters, insulators, boilermakers, maintenance mechanics, and laborers working in proximity to insulated pipe systems, represent the primary occupational groups with documented potential exposure to this product. Facilities where large-scale piping networks were present — including petrochemical plants, steel mills, paper mills, and power stations — were environments where products such as the WO-339 MC Gun were commonly used, and where multi-trade workforces could encounter asbestos-containing insulation materials during the normal course of their duties.

Bystander exposure is also a recognized pathway in litigation involving pipe insulation products of this type. Workers in adjacent trades who did not directly handle asbestos-containing materials could nonetheless inhale airborne fibers released during nearby installation or maintenance activities.

The WO-339 MC Gun is a Tier 2 litigated product. There is no established asbestos bankruptcy trust fund associated with Narco through which claims for this specific product can be filed administratively. Legal remedies for individuals harmed by exposure to this product are pursued through civil litigation in the tort system.

Litigation records document claims brought against manufacturers of asbestos-containing pipe insulation products asserting that companies knew or should have known of the health hazards associated with asbestos exposure and failed to adequately warn workers or take steps to reduce exposure risk. Plaintiffs alleged that manufacturers of products in this category, including industrial insulation compounds applied to pipe systems, continued to produce and market asbestos-containing materials during periods when the scientific and medical literature increasingly identified asbestos inhalation as a cause of serious disease.

Asbestos-related diseases documented in litigation involving pipe insulation products include mesothelioma, asbestos-related lung cancer, asbestosis, and pleural disease. These conditions typically have extended latency periods — often ranging from ten to fifty years between initial exposure and clinical diagnosis — meaning that workers exposed to products such as the WO-339 MC Gun during the 1964–1975 production window may only now be receiving diagnoses.

Individuals who believe they were exposed to the WO-339 MC Gun or similar Narco pipe insulation products, and who have received a diagnosis of an asbestos-related disease, should consult with an attorney experienced in asbestos litigation. Legal counsel can evaluate the exposure history, identify all potentially liable parties, and determine the appropriate legal venues for filing claims. In cases involving multiple asbestos-containing products and multiple manufacturers — which is common in industrial exposure cases — attorneys can pursue claims across numerous defendants simultaneously.

Surviving family members of individuals who died from asbestos-related disease following occupational exposure may have standing to bring wrongful death claims. Applicable statutes of limitations vary by jurisdiction and typically begin to run from the date of diagnosis or the date of death, not from the date of initial exposure.

This article is provided for informational and legal reference purposes. It documents a specific asbestos-containing product based on available litigation records and regulatory history. It does not constitute legal advice. Individuals with potential asbestos exposure should seek qualified legal and medical counsel.