Tree climbing with a full compliment of safety gear shows your customers and employees that you are serious about doing the job right and preserving everyone's safety. Tree climbing injuries are very unforgiving, and a few dollars spent on safety gear and standards prevents thousands in medical bills and lost productivity. Every climber should own and use (at least) a helmet, chaps, eye and hearing protection, and gloves.
The 2017 ANSI Z.133 standard covers the safety requirements for tree care operations.