Air handling units are available in different shapes and sizes. Selection of air handling units are generally based on their efficiency, maintenance, space constraints etc. The main type of air handling units are fan coils or blower coils, modular AHUs, packaged AHUs, custom AHUs etc. Custom AHU units are available in different configurations. They are most commonly used in industrial applications with harsh conditions. They are expensive but comes with a long lifespan.