In 1963, the U.S. Postal Service banned one everyday object

The Spray Can Goes Postal

On July 15, 1963, Postmaster General J. Edward Day signed Order 825, removing aerosol containers from the list of mailable matter under Title 39 of the U.S. Code. The regulation arrived without fanfare but carried immediate force: any pressurized canister—hairspray, shaving cream, deodorant, insecticide—was now contraband in the mail. Violators faced fines up to $1,000 and six months in federal prison. The move blindsided manufacturers, who had spent the previous decade convincing Americans that aerosols belonged in every bathroom and kitchen. By 1963, U.S. households bought 1.8 billion cans annually, a 400 percent jump from 1950. The Postal Service had carried them routinely since the late 1940s, when companies like Reddi-wip and Right Guard began shipping cases cross-country. But as air mail volume doubled in the early 1960s, so did the altitude—and the danger.

Pressure, Temperature, and Disaster

Aerosol cans work by storing liquids under 60 to 80 pounds per square inch of pressure, typically using propellants like butane or propane. At sea level, a steel can withstands that load easily. But commercial aircraft in 1963 cruised at 18,000 to 25,000 feet, where cabin pressure dropped to the equivalent of 8,000 feet and cargo holds went unpressurized entirely. Temperature swings compounded the risk: a can loaded in Miami at 95°F might hit minus-40°F at altitude, then warm rapidly during descent. The expansion and contraction fatigued seams. On March 8, 1962, a United Air Lines DC-7 flying from Denver to Chicago experienced a loud bang in the aft cargo bay. The crew descended immediately and discovered a ruptured hairspray can had blown a six-inch hole in an aluminum cargo liner. In November 1962, an American Airlines 707 diverted to St. Louis after a shaving cream explosion cracked a bulkhead. The Civil Aeronautics Board investigated 47 similar events between January 1961 and June 1963, with 11 causing structural damage.

The Public Didn't Notice, But Lawyers Did

The 1963 ban drew almost no press coverage. Most newspapers buried the story on inside pages, if they ran it at all. The *New York Times* gave it three paragraphs on page 58. Consumers rarely mailed aerosols anyway—bulk shipments moved by truck or rail, and individuals sent gifts via parcel services that quietly began refusing pressurized goods in late 1962. But the legal implications rippled for decades. In 1974, the Hazardous Materials Transportation Act codified the postal ban into federal law, adding aerosols to a list that included explosives, radioactive materials, and live animals. The rule survived court challenges in 1981 and 1993, with judges ruling that the Postal Service's authority to exclude dangerous articles outweighed commercial convenience. By the 1990s, online retailers and private couriers like FedEx and UPS developed specialized handling procedures for aerosols, using ground-only shipping and vented containers. The Postal Service never followed suit. Today, more than 60 years later, USPS regulations still cite Order 825: aerosol cans remain prohibited in domestic and international mail, with narrow exceptions for certain medical inhalers sent by registered pharmacies.

Why It Still Matters

The aerosol ban set the template for modern hazardous-materials law. Before 1963, the federal government regulated explosives and poisons but largely ignored consumer products that became dangerous only under specific conditions. The Postal Service's decision established that even everyday items—shampoo, whipped cream, tire inflators—could be restricted if transport conditions amplified their risk. That principle now governs everything from lithium batteries (banned from passenger aircraft cargo holds in 2016) to hand sanitizer (restricted during the COVID-19 pandemic). The 1963 rule also marked the moment when air freight overtook rail as the Postal Service's primary long-haul mode, forcing a reckoning with altitude physics that railways never faced. And it underscored a quirk of federal law: USPS remains the only U.S. shipping carrier with statutory authority to criminalize certain mailings outright, a power it uses sparingly but decisively. The aerosol ban endures not because cans still explode in mail planes—modern alloys and propellants largely solved that by the 1970s—but because the legal precedent proved too useful to dismantle.