Heat Soak Test oven: the best guarantee to prevent sudden and unexpected explosions of tempered glass sheets, due to impurities of Nickel Sulphide in the original float glass sheets. HST oven represents the ideal means to comply with the safety rules concerning the use of tempered glasses. Keraglass HST oven, certified according to the Standards DIN-EN14179-1, allows the user to enter a certified product on the market.