The SS Morro Castle disaster was one of the most influential maritime tragedies of the 20th century—and a key reason why asbestos became standard on American ships. While the 1934 fire led to crucial safety reforms in ship construction, it also helped trigger one of the largest occupational health crises in history.
The Disaster That Changed Shipbuilding
On September 8, 1934, the SS Morro Castle, a luxury liner steaming from Havana to New York, became a deathtrap when fire erupted at 2:50 a.m. in a storage locker within the First Class Writing Room. Hours after the mysterious death of Captain Robert Willmott, the blaze—possibly sparked by faulty wiring or flammable materials—tore through the ship’s wooden paneling and varnished interiors, fueled by gale-force winds. Within 20 minutes, it severed electrical cables, plunging the ship into darkness and silencing alarms. The crew, under Acting Captain William Warms, failed to close fire doors or organize firefighting efforts, and by 3:30 a.m., flames and smoke engulfed multiple decks, trapping passengers in a nightmare of searing heat and choking fumes. Only eight lifeboats launched, carrying mostly crew, while many of the 137 victims perished in flames or stormy seas.
Investigations revealed that the ship’s flammable interiors—wooden fittings, fabric upholstery, and painted surfaces—lacked firebreaks to slow the blaze’s spread. In response, Congress passed 1937 legislation mandating fireproof construction for U.S. passenger ships, including:
Firescreen bulkheads to contain blazes
Incombustible materials in passageways and staterooms to slow fire spread
Structural reinforcements to maintain hull integrity during fires
These reforms sparked a shipbuilding revolution, with asbestos emerging as the go-to fireproofing material—its promise of safety shaped by tragedies like the Morro Castle.
The Morro Castle disaster exposed the lethal flaws of flammable ship interiors, prompting Congress to enact stringent fireproofing laws in 1937. To comply, companies like Johns-Manville developed Marinite, a rigid insulation board crafted from asbestos fiber, diatomaceous silica, and inorganic binders. Marketed as “fireproof, non-corroding, and easy to erect,” Marinite was hailed as a structural and insulating marvel, capable of withstanding temperatures up to 2,000°F without a metal sheath, unlike mineral-wool alternatives. Its development was a direct response to the Morro Castle tragedy, with Johns-Manville executives noting that the fire’s devastation “gave us a chance to break into the marine fireproofing market."
Marinite’s fireproofing prowess was rigorously tested. By 1936–1937, it passed Coast Guard B-15 bulkhead requirements, enduring 1,550°F for 30 minutes while keeping the unexposed side’s temperature rise below 250°F. Trials on ships like the SS Nantasket and SS America proved its reliability, leading to its adoption across “every American-flag passenger vessel built since the early 1940s,” as well as Liberty ships and war transports. Marinite was versatile, available in densities of 23, 36, and 65 pounds per cubic foot, balancing insulation and strength for various applications.
On ships, Marinite and other asbestos-based products transformed construction:
Firescreen Bulkheads: Marinite panels formed barriers to contain blazes, critical for isolating fires like the one that raged unchecked on Morro Castle.
Joiner Panels: Used in staterooms, passageways, and crew quarters, these replaced flammable wood, reducing fuel for fires.
Insulation: Asbestos wrapped piping, structural steel, and engine rooms, preventing heat transfer that could ignite nearby materials.
Specialized Linings: Marinite lined ovens, galleys, refrigeration rooms, and electrical conduits, ensuring fire resistance in high-risk areas.
For the Morro Castle, Marinite could have been a game-changer. The fire, sparked in a storage locker and fueled by varnished wood and open stairwells, spread in minutes, cutting power and trapping passengers. Marinite bulkheads could have confined the blaze to B Deck, slowing its vertical climb. Non-combustible joiner panels in the Writing Room and passageways would have starved the fire, extending escape time. Asbestos-insulated wiring might have preserved alarms and lighting, preventing the chaos of darkness. By reducing smoke and heat, Marinite could have kept routes passable, potentially saving many of the 137 lives lost. And that's why Congress mandated the use of asbestos on ships - to save lives.
Asbestos did save lives—at least at first. Many of our Navy veterans survived shipboard fires because asbestos slowed the spread of flame. But decades later, some of those same veterans died not from battle, but from mesothelioma, lung cancer, and asbestosis—slow, suffocating deaths caused by the very material meant to protect them.
The tragedy of maritime asbestos use is that it wasn’t a life-saving breakthrough—it was a life trading breakthrough. If the asbestos industry had been open about the risks of its products, perhaps there could have been a safe way to use asbestos on ships. But there wasn't and now asbestos lurks silently on untold thousands of commercial, military, and private vessels.
Below are some of the most common asbestos applications found on U.S. Navy, merchant, and commercial ships from the 1930s through the 1970s:
Location on Ship | Typical Asbestos Use |
|---|---|
Bulkheads (walls) | Marinite panels used for fireproof partitions between sections of the ship |
Ceilings and floors | Asbestos insulation behind joiner panels in crew quarters, passageways, and stairwells |
Engine rooms | Pipe insulation, gaskets, packing, turbines, boilers—all wrapped in asbestos materials |
Living quarters | Asbestos board behind bunks, in walls, and in ventilation systems |
Kitchens and galleys | Oven linings, equipment insulation, and Marinite board to contain heat and fire risks |
Refrigerated areas | Marinite and other fireproof panels used in insulation and interior framing |
Electrical compartments | Asbestos-lined panels and sheathing used for wiring, transformers, and switchgear |
Structural steel | Asbestos board wrapped around beams and columns to meet fire safety codes |
The sheer scale of asbestos use meant that almost every maritime worker—civilian or military—was exposed in some form. It wasn’t just shipbuilders and boiler techs. It was machinists, cooks, electricians, navigators—even officers sleeping in insulated cabins.
The asbestos used on ships wasn’t just widespread—it was especially dangerous. Much of the maritime asbestos installed from the 1930s through the 1970s contained amosite, a brown amphibole fiber known for its sharp, brittle shape and greater durability in the lungs compared to chrysotile (white asbestos).
This higher toxicity, combined with the tight quarters and poor ventilation of ships, made maritime workers especially vulnerable. Scientific studies consistently show that maritime occupations carry an elevated risk of asbestos-related diseases, even among workers with relatively low or secondary exposure.
The Morro Castle burned in hours—but the policies it sparked burned through lives for decades. Asbestos reshaped shipbuilding, but at a hidden cost paid slowly, painfully, and in silence by generations of maritime workers. It didn’t just line bulkheads—it settled in lungs, waited in shadows, and stole lives under the guise of safety.
The fire changed everything. But in trying to ensure no one burned again, we unknowingly created a different kind of death sentence—one still unfolding aboard the rusting hulls of history.
