Asbestos Gaskets & Packing

Asbestos gaskets and packing were essential sealing components used in virtually every industry that involved high-temperature or high-pressure piping systems. Gaskets are flat seals placed between flanged pipe connections, valve bodies, pump housings, and equipment covers to prevent leaks of steam, hot liquids, gases, and chemicals. Packing is fibrous material compressed around valve stems and pump shafts to prevent leakage at moving joints. Both products relied heavily on chrysotile and amosite asbestos for their extraordinary heat resistance, chemical inertness, and compressibility.¹

Asbestos gaskets were ubiquitous in oil refineries, chemical processing plants, electrical power generating stations, pulp and paper mills, steel mills, and aboard naval and commercial vessels. Workers in these industries routinely cut gaskets from bulk sheet material using knives, punches, or die-cutting tools — a process that released asbestos fibers directly into the worker's breathing zone. Removing old gaskets required scraping hardened asbestos material from metal flanges, often in confined spaces with minimal ventilation.²

Major manufacturers of asbestos gaskets and packing included Garlock Sealing Technologies, John Crane Inc., A.W. Chesterton Company, and Flexitallic. These companies produced thousands of gasket sizes and configurations, from small valve bonnets to large heat exchanger covers several feet in diameter. Some asbestos gasket sheet materials contained over 80% asbestos by weight, making them among the most concentrated asbestos products in industrial use.³

The combination of high asbestos content, frequent handling, and exposure in confined industrial environments made gasket and packing work one of the most hazardous asbestos-related occupations. Workers who spent careers cutting, fitting, and replacing gaskets in refineries and power plants have been diagnosed with mesothelioma and other asbestos-related diseases at rates significantly above the general population.²

Asbestos was used in a wide variety of sealing products for industrial applications:¹

• Sheet gaskets — Flat sheets of compressed asbestos fiber in a rubber or resin binder, from which individual gaskets were cut to match specific flange dimensions. The most common form of asbestos gasket material
• Spiral-wound gaskets — Alternating layers of metal strip and asbestos filler material wound into a spiral. Used in high-pressure applications requiring both rigidity and compressibility
• Ring gaskets — Pre-cut asbestos rings for standard pipe sizes, valve bonnets, and pump housings
• Braided packing — Asbestos fibers braided into rope-like material, wrapped around valve stems and pump shafts to prevent leakage. Often lubricated with graphite or PTFE
• Millboard gaskets — Thick, rigid sheets of compressed asbestos used as gaskets and heat shields in boilers, furnaces, and ovens

Asbestos-related diseases from gasket and packing exposure produce symptoms that typically emerge decades after initial exposure:²

• Dyspnea — Progressive shortness of breath, initially during exertion and eventually at rest
• Chronic cough — Persistent cough that may produce small amounts of sputum
• Chest wall pain — Localized pain that may indicate pleural thickening or early mesothelioma
• Reduced exercise tolerance — Declining ability to perform physical activities
• Abdominal pain and distension — In cases of peritoneal mesothelioma, which may develop from ingested asbestos fibers

Gasket and packing work generated asbestos exposure through several specific activities:¹

• Cutting gaskets — Using knives, scissors, or die punches to cut gaskets from sheet material released fibers from cut edges and generated asbestos dust
• Scraping old gaskets — Removing spent gaskets from flanges required forceful scraping that pulverized dried asbestos material into airborne dust
• Packing valves — Cutting, fitting, and compressing asbestos braided packing around valve stems released fibers during handling
• Confined space work — Much gasket work occurred inside vessels, pipe galleries, and mechanical rooms with limited air circulation, concentrating airborne fibers
• Bystander exposure — Other tradespeople working near gasket operations inhaled fibers released by gasket cutting and scraping activities

Workers in the following roles and industries had elevated exposure to asbestos from gaskets and packing:²

• Refinery workers — Oil refinery maintenance workers routinely cut and replaced hundreds of asbestos gaskets during turnaround shutdowns
• Power plant workers — Boiler operators, maintenance mechanics, and turbine technicians handled asbestos gaskets in steam-generating equipment
• Chemical plant workers — Process piping in chemical plants required frequent gasket replacement due to corrosive service conditions
• Navy and maritime workers — Shipboard engineers and machinists used asbestos gaskets extensively in propulsion, auxiliary, and weapons systems
• Pipefitters and millwrights — Skilled tradespeople across many industries who installed and maintained piping systems
• Industrial maintenance workers — General maintenance mechanics in manufacturing facilities who performed valve packing and gasket replacement

Diagnostic workup for suspected gasket-related asbestos disease includes:³

• Industrial hygiene history — Detailed account of gasket and packing work, including industries, years of exposure, frequency of gasket cutting, and whether respiratory protection was available
• Chest imaging — X-ray and CT scan for pleural and parenchymal abnormalities
• Pulmonary function tests — To assess restrictive or obstructive patterns and diffusion capacity
• Biopsy — Tissue sampling when imaging suggests mesothelioma or lung cancer

Treatment follows established protocols for the specific asbestos-related diagnosis:³

• Mesothelioma — Multimodal treatment with surgery, chemotherapy, immunotherapy, and radiation as appropriate
• Lung cancer — Standard oncologic management based on type, stage, and patient fitness
• Asbestosis — Supportive care focused on symptom management, oxygen supplementation, and prevention of complications
• Pleural effusion — Drainage and pleurodesis for recurrent symptomatic fluid collections

Outcomes for workers exposed to asbestos gaskets depend on cumulative exposure and disease type:²

• Refinery cohort studies — Multiple studies of refinery workers have demonstrated elevated standardized mortality ratios for mesothelioma and lung cancer, with gasket work identified as a significant contributing exposure
• Navy veterans — Studies of shipboard personnel show particularly high mesothelioma rates, with gasket and packing work in engine rooms identified as a major exposure source
• Mesothelioma — Median survival of 12–21 months from diagnosis
• Latency — Average latency from first exposure to disease diagnosis is 30–40 years, meaning workers exposed in the 1960s and 1970s are still being diagnosed today

Modern industrial practices have largely eliminated asbestos from sealing products, but precautions remain important:¹

• Asbestos-free substitutes — Modern gaskets use PTFE, graphite, mineral fiber, aramid (Kevlar), and other non-asbestos materials that provide equivalent or superior sealing performance
• Material verification — Before performing gasket or packing work in older facilities, verify that existing materials do not contain asbestos through testing or documentation
• Wet methods — When working with known or suspected asbestos gaskets, wet the material before cutting, scraping, or removing to minimize fiber release
• Respiratory protection — Use appropriate NIOSH-approved respirators when exposure to asbestos gasket material is possible
• Proper waste handling — Dispose of old asbestos gasket material in sealed, labeled containers in accordance with applicable regulations