¹ 1 The actual minimum distance to combustible materials from the outer surface of a chimney must be defined according to the designation of the chimney, as described in their marking. and national legal acts. If the legal acts and chimney technical specifications indicate different admissible distances of the combustible materials, it is necessary to select the higher distance. The minimal distance to combustible materials were determined using 200 mm diameter chimneys. The distance to combustible materials for chimneys larger than tested must be increased by a factor. For dn 201-300 mm the factor must be 1 time the distance to combustible material determined for dn 200 mm, for dn 301-450 mm – 1,5, dn 451-600 mm – 2, above dn 601 mm – 4.