Section 658-10-3 - Use of Existing Chimneys10.3.1 Except as provided in Section 10.3.1.1, the required 2" minimum clearance to combustible material for existing interior chimneys and the required 1" minimum clearance to combustible material for existing exterior chimneys is not required when replacing oil- or gas-fired appliances. 10.3.1.1 The 2" clearance to combustible material for existing interior chimneys and the 1" minimum clearance to combustible material for existing exterior chimneys are required when a solid fuel appliance or a wood stove is connected to the chimney flue.10.3.2 When installing any gas, oil or solid fuel appliance, the chimney must be lined with a clay tile liner or listed lining system compatible with the intended fuel source.02-658 C.M.R. ch. 10, § 3