Air Contaminants And Industrial Hygiene Ventilation Pdf
File Name: air contaminants and industrial hygiene ventilation .zip
Ambient air contaminants have different adverse effects on human health, environment, and structures.
Easy-to-read, question-and-answer fact sheets covering a wide range of workplace health and safety topics, from hazards to diseases to ergonomics to workplace promotion. Download the free OSH Answers app. Search all fact sheets:. This document is an introduction to industrial ventilation.
Industrial Hygiene Engineering
Traditionally, nonindustrial ventilation systems commonly known as heating, ventilating, and air-conditioning HVAC systems were built to control temperature, humidity, and odors.
For example, a large local exhaust system may also serve as a dilution system, and the HVAC system may serve as a makeup air system see Appendix III for a primer and Appendix III for an explanation of these terms.
This section of the manual addresses ventilation in commercial buildings and industrial facilities. Indoor Air Contaminants include but are not limited to particulates, pollen, microbial agents, and organic toxins. These can be transported by the ventilation system or originate in the following parts of the ventilation system:.
People exposed to these agents may develop signs and symptoms related to "humidifier fever," "humidifier lung," or "air conditioner lung. Volatile Organic and Reactive Chemicals for example, formaldehyde often contribute to indoor air contamination. The facility's ventilation system may transport reactive chemicals from a source area to other parts of the building. Tobacco smoke contains a number of organic and reactive chemicals and is often carried this way. In some instances the contaminant source may be the outside air.
Outside air for ventilation or makeup air for exhaust systems may bring contaminants into the workplace e. AMCA is a trade association that has developed standards and testing procedures for fans. ASHRAE is a society of heating and air conditioning engineers that has produced, through consensus, a number of standards related to indoor air quality, filter performance and testing, and HVAC systems. ANSI has produced several important standards on ventilation, including ventilation for paintspray booths, grinding exhaust hoods, and open-surface tank exhausts.
It sets standards for ducts and duct installation. NFPA has produced a number of recommendations which become requirements when adopted by local fire agencies , e. In addition, many OSHA health standards include ventilation requirements. The four standards in 29 CFR Workplace investigations of ventilation systems may be initiated by worker complaints of possible overexposures to air contaminants, possible risk of fire or explosion from flammable gas or vapor levels at or near the lower explosive limit LEL , or indoor air quality complaints.
The second phase of the investigation involves an examination of the ventilation system's physical and operating characteristics. Common faulty ventilation conditions and their probable causes are listed in Table III Specific points to consider during any investigation of a ventilation system include emission source, air behavior, and employee involvement.
Points that should be included in a review of operational efficacy are shown in Table III Appendix III contains information on points to be checked in a troublesome exhaust system. The characteristics of the ventilation system that must be documented during an investigation include equipment operability, physical measurements of the system, and use practices. Before taking velocity or pressure measurements, note and record the operating status of the equipment.
For example, are filters loaded or clean? Are variable-flow devices like dampers, variable-frequency drives, or inlet vanes in use? Are make-up units operating? Are system blueprints available? Squeeze off a quick burst of smoke. Time the smoke plume's travel over a two-foot distance.
Calculate the velocity in feet per minute. For example, if it takes two seconds for the smoke to travel two feet, the velocity is 60 fpm.
Hood static pressures SPH should be measured about duct diameters downstream in a straight section of the hood take-off duct. The measurement can be made with a pitot tube or by a static pressure tap into the duct sheet metal see Figure III Figure III The approximate relationship of capture velocity V c to duct velocity V d for a simple plain or narrow flanged hood is illustrated in Figure III At two duct diameters from the hood opening, capture velocity decreases by a factor of 10, to 30 fpm.
Figure III shows a rule of thumb that can be used with simple capture hoods. If the duct diameter D is 6 inches, then the maximum distance of the emission source from the hood should not exceed 9 in. Similarly, the minimum capture velocity should not be less than 50 fpm. Use of the six-and-three rule ensures better design by providing for a minimum loss at six diameters of straight duct at the fan inlet and a minimum loss at three diameters of straight duct at the fan outlet Figure II Stack height should be 10 ft higher than any roof line or air intake located within 50 ft of the stack Figure III For example, a stack placed 30 ft away from an air intake should be at least 10 ft higher than the center of the intake.
A well-designed system and a continuing preventive maintenance program are key elements in the prevention and control of ventilation system problems.
If you suspect microbial agents, check for stagnant water in the ventilation system. The presence of mold or slime is a possible sign of trouble.
Table III lists preventive measures for controlling microbial problems in ventilation systems. If an organic or reactive chemical e. OSHA has published a proposed rule for IAQ including tobacco smoke in the workplace , and this rulemaking is likely to be completed in the near future.
Smoking policies should include provisions for dedicated smoking areas. Dedicated smoking areas should be configured so that migration of smoke into nonsmoking areas will not occur. Such areas should:. Industrial Ventilation, a Manual of Recommended Practice. Handbooks and Standards. Burgess, W.
Ventilation and Control of the Work Environment. New York: Wiley Interscience. Guidance for Indoor Air Quality Investigations. Washington, D. Government Printing Office. Before an appropriate ventilation system can be selected, the employer should study emission sources, worker behavior, and air movement in the area. In some cases the employer may wish to seek the services of an experienced professional ventilation engineer to assist in the data gathering.
Table III shows factors to consider when selecting a ventilation system. Combinations of controls are often employed for HVAC purposes. General exhaust ventilation, also called dilution ventilation, is different from local exhaust ventilation because instead of capturing emissions at their source and removing them from the air, general exhaust ventilation allows the contaminant to be emitted into the workplace air and then dilutes the concentration of the contaminant to an acceptable level e.
Dilution systems are often used to control evaporated liquids. To determine the correct volume flow rate for dilution Q d , it is necessary to estimate the evaporation rate of the contaminant q d according to the following equation:. The number of air changes per hour is the number of times one volume of air is replaced in the space per hour.
In practice, replacement depends on mixing efficiency. When using dilution ventilation:. A typical local exhaust ventilation system is composed of five parts: fans, hoods, ducts, air cleaners, and stacks. Local exhaust ventilation is designed to capture an emitted contaminant at or near its source, before the contaminant has a chance to disperse into the workplace air.
Fan Selection. To choose the proper fan for a ventilation system, this information must be known:. Once this information is available, the type of fan best suited for the system can be chosen.
Many different fans are available, although they all fall into one of two classes: axial flow fans and centrifugal fans. The hood captures, contains, or receives contaminants generated at an emission source. The hood converts duct static pressure to velocity pressure and hood entry losses e.
A hood's ability to convert static pressure to velocity pressure is given by the coefficient of entry C e , as follows:. To minimize air-flow requirements, the operation should be enclosed as much as possible, either with a ventilated enclosure, side baffles, or curtains. This helps both to contain the material and to minimize the effect of room air.
When using a capture or receiving hood, the hood should be located as close to the contaminant source as possible. Reducing the amount of contaminants generated or released from the process reduces ventilation requirements.
The hood should be designed to achieve good air distribution into the hood openings so that all the air drawn into the hood helps to control contaminants. Avoid designs that require that the velocities through some openings be very high in order to develop the minimum acceptable velocity through other openings or parts of the hood. The purpose of most ventilation systems is to prevent worker inhalation of contaminants.
For this reason, the hood should be located so that contaminants are not drawn through the worker's breathing zone. This is especially important where workers lean over an operation such as an open-surface tank or welding bench. Most hood design recommendations account for cross-drafts that interfere with hood operation. Standard hood designs may not be adequate to contain highly toxic materials.
The hood should be designed to cause minimum interference with the performance of work. Positioning access doors inside an enclosure that must be opened and closed often means that in practice the doors will be left open, and locating capture hoods too close to the process for the worker's convenience often means that the hood will be disassembled and removed.
Hoods should never increase the likelihood of mechanical injury by interfering with a worker's freedom to move around machinery. Air flows turbulently through ducts at between 2,, feet per minute fpm. Ducts can be made of galvanized metal, fiberglass, plastic, and concrete.
Industrial Air Pollution Control
Many work processes create harmful dusts, vapours and fumes that contaminate the air. This guidance is for persons conducting a business or undertaking PCBUs. It explains some factors to consider when selecting, using and maintaining a local exhaust ventilation LEV system. Under the Health and Safety at Work Act HSWA , you must ensure the health and safety of workers and that others are not put at risk from your work. You must eliminate risks so far as is reasonably practicable. Exposure monitoring allows you to see if your controls are effective or if there are additional areas where you need to put controls in place.
Provides an advanced level of study of industrial hygiene engineering situations with emphasis on the control of exposure to occupational health hazards. Primary attention is given to ventilation, noise and vibration control, heat stress and industrial illumination. Other topics include industrial water quality, solid waste control, handling and storage of hazardous materials, personal protective equipment, and costs of industrial hygiene control. We are always looking for ways to improve customer experience on Elsevier. We would like to ask you for a moment of your time to fill in a short questionnaire, at the end of your visit. If you decide to participate, a new browser tab will open so you can complete the survey after you have completed your visit to this website.
of industrial hygiene, industrial ventilation, and air pollution control. Hood: A shaped inlet designed to capture contaminated air and conduct it into the exhaust.
To provide a healthy and comfortable environment, ventilation is necessary in every human occupancy; it is the one industrial hygiene control that is always required, and every occupational health and safety professional needs to know how to apply and manage it. But how do we know when we or others have the ventilation right? The best way is to compare existing or planned conditions and equipment with established standards of good practice. When we use and follow recognized SGP, we are more likely to provide better employee health and comfort, enhance performance, minimize costs, and protect ourselves from legal actions such as OSHA citations and third-party lawsuits.
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The industrial hygienist is actively involved with the engineering community, particularly where the subject of industrial ventilation is concerned. While engin.