Chinese gas water heaters have gone through five stages: direct exhaust, flue, forced exhaust, balance, and outdoor. Each step is a technological breakthrough, and it is a step forward in the "safety" and "comfort" of bathing. Among them, the direct-discharge water heater completed its historical mission in June 2000 and was forcibly banned from sales and use by the state; China’s gas water heater implementation standards have also experienced four standards: "86 standards, 94 standards, 2001 standards, and 2015 standards". An update of the standard marks a new step in the design and manufacture of gas water heaters in China, and it also raises the barriers to entry for the industry.
