Related Commercial Resources CHAPTER 30 INDUSTRIAL LOCAL EXHAUST SYSTEMS Local Exhaust Fundamentals. 30.3 Air Movement in Vicinity of Local Exhaust. 30.5 Other Local Exhaust System Components. 30.8 I NDUSTRIAL exhaust ventilation systems collect and remove airborne contaminants consisting of particulate matter (dust, fumes, smokes, fibers), vapors, and gases that can create a hazardous, unhealthy, or undesirable atmosphere.
† Capacity in accordance with DOE test procedures. Ratings are position dependent. Traditional single-source heating system. The heat pump also. Enhancement for select Carrier air conditioner or heat pump systems. It uses less electrical power than its PSC counterpart and also has a wider range of speeds. These books cover procedures for HVAC service, installation, and maintenance. This reference handbook covers the installation procedures encountered in residential and light commercial HVAC systems. The book is printed on specially coated paper so it may be kept as a resource in the service truck. Carrier University, Bynum Training.
Exhaust systems can also salvage usable material, improve plant housekeeping, and capture and remove excessive heat or moisture. Often, industrial ventilation exhaust systems are considered life-safety systems and can contain hazardous gases and/or particles. Industrial exhaust systems also have to comply with ANSI/ ASHRAE Standard 62.1-2004 and other standards as required e.g., by the National Fire Protection Agency (NFPA). Local Exhaust Versus General Ventilation Local exhaust ventilation systems can be the most cost-effective method of controlling air pollutants and excessive heat. For many manual operations, capturing pollutants at or near their source is the only way to ensure compliance with threshold limit values (TLVs) in the worker’s worker’s breathing zone. Local exhaust ventilation optimizes ventilation exhaust airflow, airflow, thus optimizing system operating costs.
In some industrial ventilation designs, the emphasis is on filtering air captured by local exhausts before exhausting it to the outdoors or returning it to the production space. As a result, these systems are evaluated by filter efficiency or total particulate removal.
However, if only a small percentage of emissions are captured, the degree of separation efficiency sometimes becomes irrelevant. For a process exhaust system in the United States, the design engineer must verify if the system is permitted by the 1990 Clean Air Act. For more information, see the Environmental Protection Agency’s Web site (www.epa.gov).
The pollutant-capturing efficiency of local ventilation systems depends on hood design, the hood’s position relativ relativee to the source of contamination, temperature of the source being exhausted, and exhaust airflow. Selection and position of the hood significantly influence initial and operating costs of both local and general ventilation systems. In addition, poorly designed and maintained local ventilation systems can cause deterioration of building structures and equipment, negative health effects, and decreased worker productivity. No local exhaust ventilation system is 100% effective in capturing pollutants and/or excess heat. In addition, installation of local exhaust ventilation system may not be possible in some circumstances, because of the size or mobility of the process.
In these situations, general ventilation is needed to dilute pollutants and/or excess heat (where pollutants are toxic or present a health risk to workers, dilution ventilation should be avoided). Air supplied by the general ventilation system is usually heated and can be conditioned. Supply air replaces air extracted by local and general exhaust systems and improves comfort conditions in the occupied zone. Chapter 12 of the 2005 ASHRAE Handbook—Fundamentals covers definitions, particle sizes, allowable concentrations, and upper The preparation of this chapter is assigned to TC 5.8, Industrial Ventilation Systems. Copyright © 2007, ASHRAE and lower explosive limits of various air contaminants.
Chapter 29 of this volume, Goodfellow and Tahti (2001), and Chapter 2 of Industrial Ventilation: A Manual of Recommended Practice (American Conference of Governmental Industrial Hygienists ACGIH 2004) detail steps to determine air volumes necessary to dilute contaminant concentration using general ventilations. Sufficient makeup air must be provided to replace air removed by the exhaust system. If replacement air is insufficient, insufficient, building pressure becomes negative relative to atmospheric pressure. Negative building pressure allows air to infiltrate through open doors, window cracks, and backfeed through combustion equipment vents. As little negative pressure as 0.05 in. Of water can cause drafts and might cause backdrafts in combustion vents, thereby creating a potential health hazard. Negative plant pressure can also cause excessive excessive energy use.
If workers near the plant perimeter complain about cold drafts, unit heaters are often installed. Heat from these units often is drawn into the plant interior, overheating the interior. Too often, this overheating is addressed by exhausting more air from the interior, causing increased negative pressure and more infiltration. Negative Negative plant pressure reduces the exhaust volumetric flow rate because of increased system resistance, which can also decrease local exhaust efficiencies. Wind effects on building balance are discussed in Chapter 16 of the 2005 ASHRAE Handbook— Fundamentals. Positive-pressure plants and balanced balanc ed plants (those with equal exhaust and replacement replacemen t air rates) use less le ss energy. However, However, if there are clean and contaminated zones in the same building, excessive supply airflow in contaminated zones can cause contaminants to move from the contaminated zone into clean(er) zones, which is undesirable.
Exhaust system discharge may be regulated under various federal, state, and local air pollution control regulations regulations or ordinances. These regulations may require exhaust air treatment before discharge to the atmosphere. Chapter 25 of the 2004 ASHRAE Handbook—HVAC Systems and Equipment provides guidance and recommendations for discharge air treatment.