It includes the electrotechnical, heating, ventilating, air conditioning, refrigeration and plumbing industries. Through its services division, Direct Energy installs and services heating, ventilating and air conditioning equipment. Diffusers are very common in heating, ventilating, and air-conditioning systems. Variable air volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system. Upgrades of fire safety, security, telecommunications, and heating, air conditioning, and ventilating systems accompanied alterations. Standard for the Installation of Air Conditioning and Ventilating Systems. Each room was connected to a flue, exhausting into a stack ventilating smoke. The Saran ventilating mesh insole was also used in the M-1945 tropical combat boot. Ventilating a space with fresh air aims to avoid "bad air". Some units can also give timing reminders for performing compressions, ventilating and changing operators. Two generators, driven by two engines, were used for jacking, steering, lighting, and ventilating. The motor should be as high as possible without ventilating or loss of water pressure. Methods for ventilating a building may be divided into "mechanical/forced" and "natural" types. Directly ventilating clothing is therefore far more efficient. The importance of high quality CPR (sufficient rate and depth without excessively ventilating) was emphasized.