First NFL Helmet Rules

• NFL helmet rules weren't actually on the books when the National Football League was founded in 1920. In fact, the use of helmets, leather or otherwise, was completely optional until 1943.
  
  

First Use of Facemasks

• In the 1950s, Cleveland Browns quarterback Otto Graham is believed to have worn the first face mask in NFL history. In 1956, the league made grabbing an opponent's face mask illegal.
  
  

The Deacon Jones Rule

• The head slap, which was popularized by NFL Hall of Famer Deacon Jones, was a move in which a defensive lineman would give a hard slap to the helmet of the offensive lineman trying to block him. This disoriented the blocker and allowed the defensive player easier access to the quarterback. The move was banned in 1977.
  
  

The Erik Williams Rule

• NFL helmet rules also prohibit offensive linemen from taking their hands and thrusting them up into the face mask of a defensive player's helmet. The rule, named for the former Dallas Cowboys tackle who perfected the technique, was established in 1997.
  
  

Other Helmet Related Penalties

• According to NFL helmet rules, a player who illegally uses the top of his helmet as a weapon, removes his helmet on the field of play (except when injured) or attacks the head of the quarterback will be hit with a 15-yard penalty. Using a helmet that is not being worn as a weapon results in a 15-yard penalty and automatic disqualification from the game.
  
  

Additional Helmet Rules

• According to current NFL helmet rules, players may only wear clear visors, not colored ones, unless they have league approval. Furthermore, one offensive player and one defensive player with communication headsets in their helmets may be on the field at a time, and they must have green dots on the back of the helmet to signify the fact that they can receive instructions from the coaching staff.