Did you know that hard hats emerged out of the first world war out of necessity to protect soldiers from heavy artillery and bombing?  Edward W. Bullard streamlined an affordable post war hard hat available in the U.S.  It was called the hard boiled hat and made out of canvas and leather head gear.  They originally targeted mining industries in California, Nevada, and Arizona.  "Bullard, who received 13 patents for his inventions, soon created new versions of his hat with adaptations for different uses. One included a device to hold carbide lamps made by his company so miners could find their way through dark underground tunnels."  Back then it was a choice left up to workers if they wanted a hard hat.  Construction of the Hoover Dam saw changes in safety policies that made the hard hat mandatory.  The Bullard company eventually shifted its industry from providing mining equipment to primarily dealing in worker protection apparel.  It seems to be implied in the article that this pushed them to begin exploring supplied air systems as well.  E.D. Bullard Co. "...introduced its first hard hat in thermoplastic in 1952 and began transitioning to polyethylene in the 1960s. All safety helmets have have been made from the plastic since the early 2000s."  Hard hats today retail at around $10 - $25 dollars.  They started out retailing for only $3, which is more equivalent to $45 today adjusting for inflation.  According to Hexa Research referenced in the article with link listed below, "...global sales of safety helmets reached an estimated $2.1 billion in 2016. Projections call for continued growth through 2025—all thanks to the inspirational efforts of Edward W. Bullard."

All information above paraphrased and taken from the link provided below.  See original article, and all credit goes to the Smithsonian Magazine and author David Kindy.  Additional link to Hexa Research provided through the link in the Smithsonian article.  https://www.hexaresearch.com/    

https://www.smithsonianmag.com/innovation/history-...