Due to the fact that the thermal insulation work fell on the winters, the Bronya Zima modification was used on the highways and at the heating unit. The welded seams have been pretreated with an anti-corrosion coating. The layer thickness was 2 mm.
In the conditions of limited space, it was impossible to use any other insulation, while a huge number of curved sections would have excluded a dense and sealed thermal insulation device.