This article discusses two main types of air conditioning systems in office buildings: local and centralized systems. Since equipment developers, customers and users have different requirements for the design, installation and operation of air conditioning systems in office buildings, depending on the workload of buildings, location, external conditions, as well as space-planning solutions, air conditioning systems currently come in different types and configurations. Reliable knowledge of classification and the ability to distinguish one system from another is key when choosing the right air conditioning system for the customer. To form a proper understanding of the systems discussed, it is necessary to understand some of the basic terminology and principles of air conditioning systems. These include methods for system design criteria, load calculations (tangible and latent thermal loads, penetration loads, equipment and appliance loads, and air conditioning system requirements). © Published under licence by IOP Publishing Ltd.