The following is intended to provide guidance in identifying field problems. Whenever a heat exchanger or heat exchanger system is not performing, the cause must be identified before a solution can be proposed. Locating the cause is seldom easy often requiring a great deal of time, more likely weeks than days, and more than management would like to provide. Problems are less frequent when plate or double-pipe exchangers are used probably because these are seldom used in low pressure gas applications such as air cooling. Here are time consuming situations. Consider a large shell-and-tube exchanger that is thought to be the cause of a problem. It may take eight hours to disassemble and longer if positioned in a difficult area to access. After disassembly one may learn it was not the cause of the problem. Duct problems may be difficult because components may not be easily accessible due to elevation or because they are mounted behind a wall or false ceiling. Two months can pass before the cause of a problem is identified including those occurring in screen rooms and racks serving as ducts.