Deputy commissioner Bill Daly said the NHL is warning teams against taking warmups without helmets, a growing trend this season that violates NHL rules.
Daly told ESPN that the league is sending out a memo to remind teams that helmets are mandatory in warmups for "all players who entered the NHL beginning with the 2019-2020 season or later," per Rule 9.6.
The Ottawa Senators skated out for warmups without helmets in a game at the Vegas Golden Knights last Wednesday, having lost in their past six trips to T-Mobile Arena. Forward Shane Pinto told TSN that the players decided at a team dinner to change their Vegas luck by doffing their helmets. "It was pretty cool to do," he said.
The Senators won the game 4-3 in a shootout.
The San Jose Sharks also went without helmets in warmups

ESPN NHL Headlines

NHL
The Oregonian Public Safety
St. Louis Post-Dispatch
Aberdeen News
NHL Montréal Canadiens
KSL 5 TV
Newsday
AlterNet