HVAC systems for laboratories are one of the most important parts of the building in terms of health, safety, and comfort of the occupants. The complexity and cost of laboratory HVAC systems and the major impact they have on building design emphasizes the need for well-defined mechanical concepts. At a minimum, the HVAC engineer must support the architectural effort during conceptual design. In addition to this role, the engineer can provide more leadership to influence the early planning of a facility by establishing mechanical system philosophies and criteria such as design criteria (temperature & humidity conditions); utility loads; zoning (grouping of air-handling systems); space allocation; and utility distribution. This article discusses the significance HVAC systems have on a laboratory building and the importance of early engineering design activities and the level of deliverables to be provided during conceptual design.