If you are an employer purchasing safety boots for your employees, you should pay VAT at the prevailing rate. You are in the correct section of our website.
If you're ordering safety boots for your own work use, you are exempt from paying VAT and you should order from the “Safety Footwear for Individuals” section - go to SS819
HMRC Reference:Notice 701/23(May 2011) is where all the detail is, should you want to read it through.