MECHANICAL VENTILATION AND EQUIPMENT
Mechanical ventilation systems for controlling conditions in individual zones can move a constant or variable supply of conditioned air to handle all or some of the heating and cooling loads. They are classified as all-air, air-water, and all-water systems. All-air systems include single-duct, dual-duct and multizone. The systems can be designed to operate at Constant Air Volume (CAV) or Variable Air Volume (VAV). Air-water and all-water systems are categorized as two-, threeand four-pipe. The Air Handling Unit (AHU) is the main air conditioning and treatment equipment. A typical AHU consists of a single volume unit with a supply fan, heating coil, cooling coil, humidifier where necessary, filters, mixed air economizer dampers, and sound attenuator. The air distribution is a key element for the successful operation of central systems to deliver the air to the conditioned spaces in an efficient way, satisfying the indoor environmental conditions as economically as possible. The air is then distributed by the ductwork and is delivered by the air-diffusion outlets. Proper circulation and exhaust must satisfy the indoor environmental quality. Mechanical ventilation systems provide great flexibility for controlling the indoor conditions, if properly designed, installed, commissioned, operated, and maintained. Proper controls can optimize their use, enhance flexibility, and improve energy efficiency. On the other hand, poor design, installation, and performance can lead to serious Indoor Air Quality (IAQ) problems, and cause thermal and acoustical discomfort, with a high energy cost.
Diagnostics for Outdoor Air Ventilation and Economizers
Today, most problems with building systems are detected as a result of occupant complaints or alarms provided by building automation systems. Building operators often respond by checking space temperatures or adjusting setpoints (or thermostat settings). The root causes of operation problems not diagnosed, so problems reoccur and the operator responds by making another adjustment. The BACnet TM standard will contribute to easier implementation by providing a standard mechanism for communication between diagnostic software and devices.
Evaluation of Quantum II microbiology system for identification of gram-negative bacteria of veterinary origin
The ability of a rapid, semiautomated bacterial identification system, the Quantum II microbiology system (Abbott Laboratories, Irving, Tex.), to accurately identify gram-negative bacteria from veterinary sources was evaluated. A total of 378 isolates were tested, including 298 organisms in the family Enterobacteriaceae and strains representing Acinetobacter sp., Aeromonas sp., Flavobacterium sp., Pasteurella multocida, Plesiomonas sp., and Pseudomonas spp. Of these isolates, 333 (88.1%) were correctly identified, 20 (5.3%) were not identified, 10 (2.6%) were incorrectly identified at the genus level, and 15 (4.0%) were incorrectly identified at the species level. The Quantum II system correctly identified 268 (89.9%) of the isolates of Enterobacteriaceae and 65 (81.3%) of the nonenteric isolates. P. multocida was not identified correctly, and some nonenteric gram-negative bacteria of clinical significance in veterinary medicine are not included in the data base. The Quantum II system provided an accurate identification system for isolates of Enterobacteriaceae but had limited usefulness for the identification of other gram-negative bacteria of clinical significance in veterinary medicine.