Indoor air pollution
Health effects associated with indoor air pollution include asthma, allergies, cancer, respiratory and heart disease, and premature death, not to mention short-term irritant effects. Indoor air quality problems may also result in increased employee sick days, higher employee turnover, decreased productivity, and attitude and morale problems â€” in addition to legal ramifications.
Though these pollutants can never be fully eliminated, they can be reduced and controlled to within safe and legal limits. Maybe itâ€™s time to evaluate your own workplace situation and find the appropriate solution to control and reduce harmful particulates within your environment.
Know the lawFirst, you must know what the law allows, and how air quality is measured. In most cases, indoor industrial air quality is governed by regulations set by OSHA. Penalties for not complying include fines, jail terms and/or legal action and increased insurance rates.
OSHA rules list exposure limits for more than 500 regulated substances. These are substances routinely found in industrial manufacturing operations that, through exposure, can create unsafe working environments.
Contaminant particles are measured in microns. One micron is 1/25,400 of an inch. For perspective, the dot on this â€œiâ€ is 397 microns. Airborne particles have diameters ranging from 0.001 to 100 microns. Individual particles 10 microns or smaller, referred to as â€œrespirable,â€ are the most harmful to human health as they can bypass the bodyâ€™s natural filtration mechanisms, enter the lungs and bloodstream and remain there permanently.
Know what youâ€™re generatingSecond, you must know the type and size of contaminants you are generating. To determine how to collect these potentially harmful airborne pollutants it is important to understand their properties. Different manufacturing operations create different types of contaminants. For example, arc and flame cutting generate dry metal oxides, while buffing and polishing operations create process dusts ranging from small coarse spheres to elongated fibers.
Since the method for collecting these contaminants also varies, size of the contaminant is important, as well. Generally speaking, welding and metal spraying operations typically yield contaminants measuring 0.01-10 microns. Bulk powder mixing and conveying operations, including cement dust and foundry dust, typically produce contaminants measuring 10-100 microns. Water-soluble machining operations produce mists or overspray with contaminants measuring 10-100 microns.
Select a solutionThe most practical way to control breathable particles, or those smaller than 10 microns, is with two-stage electrostatic precipitator air cleaning systems or reverse pulse cartridge dust collector systems. The preferred way to filter and capture industrial dusts 10 microns and larger is with mechanical filtration devices.
Electrostatic precipitators are also known as electronic air cleaners. A two-stage electrostatic precipitator has a charging section and a collection section. The charging section contains an ionizer that gives particles in the air a high positive charge as dirty air passes through the unit, attracting them to alternately charged plates in the collecting cell. Both the collecting cell and ionizer are cleaned on a regular basis.
Mechanical filter air cleaners are designed primarily for â€œdryâ€ industrial dusts. Mechanical filter systems capture dust at the closest possible point to its generation (source capture) or by filtering dust in an open air space (ambient). The most common mechanical filtration systems are cartridge filter, cyclone collector, bag house and media fan/filter.
Continuous cleaning cartridge filter units use pleated paper or polyester cartridge filters. The filter elements are cleaned online during the dust collection process. Cartridge units offer high filtration efficiency and are capable of trapping up to 99 percent of sub-micronic materials and virtually 100 percent of larger dust particles. Selecting the right sized unit is done using a simple air-to-media ratio based on the type of contaminant.
Cyclones are the oldest type of dust collection device. They operate by spinning the collected material within the device using centrifugal force to direct the dust to the outside wall of the separator. Gravity and mechanical internal deflectors direct the dust-laden air in a downward spiral and discharge the dust out the cone bottom. They can also be used as a pre-separator for heavy concentration levels.
A bag house dust collector is a tubular bag device that, like the cartridge filter units, can be cleaned online during the dust collection process. This results in a relatively constant airflow and energy saving benefits. These devices are highly efficient in the collection of fibrous and other large size process particulate at relatively high concentration levels.
A self-contained media fan/filter unit is the simplest form of industrial filtration device. It works by passing contaminated air through a prefilter where larger particles are collected, then through a primary filter where smaller particles can be captured. The clean air is then returned to the workplace.
System typesThere are other decisions to make, including whether you want a source capture system or an unducted system.
Source capture systems collect contaminants directly at the point of generation. This technique can be critical where the contaminant represents a respiratory hazard to the employee.
Unducted air cleaning systems consist of one or more air cleaning units positioned in the overhead plant space to create a planned air circulation pattern. This method effectively cleans the overall ambient plant air. Rather than eliminating the contaminant at the point of generation, as is done in source capture systems, the objective of this method is to achieve a substantial reduction in steady-state contaminant concentrations.
In most industrial settings, there are likely to be multiple manufacturing processes under one roof and multiple pollution sources, each creating its own problem. This can result in the need for a combination of filtration technologies and air control measures.