$~~~~$A hard hat is a helmet used mostly at worksites to protect the head from injuries due to falling objects. Since its introduction in the early 20th century, the headgear has saved countless lives and is considered the number one safety tool for construction workers.
$~~~~$The hard hat was invented in 1919 by Edward W. Bullard, who had just returned from World War I. Before the war, workers used to smear their hats with coal tar for protection of their head. Bullard, having witnessed the life-saving power of the metal helmet in the War, decided to produce a head protection device that was affordable for every worker and lightweight enough to be worn all day long. The Hard Boiled Hat was thus born, using steamed canvas and leather, covered with black paint, and featuring a suspension system to reduce impact. Soon, hard hats became widely used. The headgear was later made mandatory at construction sites in major construction projects, such as the Hoover Dam in 1931 and the Golden Gate Bridge in 1933.
$~~~~$Over the past century, hard hats have advanced considerably, evolving from canvas and leather to aluminum, fiberglass, and, eventually, to thermoplastic. Recently, new models have been introduced and accessories added to meet the needs of laborers working on various job sites. For instance, a ventilated hard hat was developed to keep wearers cooler, and see-through face shields were attached to better see the hazards lurking above. Today, attachments include radios, sensors, cameras, and a lot more. A common color code has also been developed for recognizing people and their roles on site. Yellow is used for general laborers and contractors, white (or sometimes black) for supervisors and managers, and green for inspectors and new workers.
$~~~~$New products continue to expand the market. Global sales of hard hats totaled USD 2.1 billion in 2016, and are expected to reach USD 3.19 billion in 2025.