Having reliable airlock seals is important to maintain production rates, but it is especially important when performing dense packing. The seals need to maintain pressure. A tear, chip or crack in a seal will result in degraded performance. So, the question is, “What is better: Rubber or Urethane seals?”
Frankly, either material is fine and the contractor who blows attics and does not perform dense packing will not notice a difference even if the seals have minor issues. However, the contractor who performs dense packing will definitely need to make sure that the seals are in top condition.
Rubber Seals: Cool Machines uses rubber seals in all of their machines. These seals are double-ply rubber. It is the same material used for conveyor belts. These seals are very durable and have great life. For the larger units (CM2400, CM3500, CM300), the seals are Rhinohide which has an extra tough surface. You can expect these seals to last for a few years. If you are dense packing, nearly every day, then you can expect to change the seals twice a year.
Urethane Seals: These seals have nearly the same life-span of rubber seals. For that reason, there is virtually no difference. However, these seals do not have the same expansion properties in colder climates. They will develop fissures and cracks in cold environments. So, the only negative is that cold weather will shorten the life-span of a urethane seal.