Complex sentence: The 1969 and 1971 refits did improve conditions, although there was little scope for upgrade, and the system was still inadequate: temperatures inside the ship continued to reach over, and on one occasion a hold reached.
Split into simpler sentences: The 1969 and 1971 refits did improve conditions, although there was little scope for upgrade, and the system was still inadequate. Temperatures inside the ship continued to reach over, and on one occasion a hold reached.