JLC · AUGUST 1989 Zero-clearance in name only, these products require careful attention to manufacturers' specs and details. Factory-built fireplaces can offer the warmth and romantic appeal of a traditional fireplace, versatility of designs, and economy. Installation is straightforward, but requires familiarity with manufacturers' standards and some basic engineering. The manufacturers and models vary significantly, so no single set of instructions can cover all factory-built fireplaces. But some guidelines, which I'll cover here, are universally applicable to all factory-built systems. Manufacturing Standards All factory-built fireplace models are designed and tested to conform to the Underwriters Laboratories Inc. safety standard UL 127 for factorybuilt fireplaces. UL 127, which is uniformly accepted as the standard guide by all major model-code groups, is the basis for the manufacturer's installation