Many HVAC technicians falsely believe that the only type of filter to use in a system is a fiberglass one-month “throwaway.” They are convinced that the only purpose of a filter is to protect the equipment from dust and debris and that the need for the better air flow provided by the fiberglass filter overrides … More
Articles
How Concerned Should We Be with the Filtration of Sub-micron Sized Particles in Indoor Environments?
In recent years more and more studies have been published showing that increased levels of sub-micron sized particles in the air result in higher levels of inflammation. This inflammation has been found in the cardiovascular and the respiratory system of exposed individuals resulting in increased morbidity and mortality. Increased levels of heart attacks and asthma attacks … More
Comparing the Efficiency of Different Types of MERV 8 Air Filters in a Room Environment
There has been a great deal of discussion about the accuracy of filter testing. This discussion has covered everything from materials (test dust) to methods to reproducibility and much more. But the problem with these discussions is that they do not deal with the effectiveness of filters in indoor environments. After all, particles in an indoor … More
What Happens to the Particles When You Sneeze?
Particles settle out of the air at different rates depending on the size of the particle. These tests show the relative exposure from particles at different distances from the source. To determine what happens to aerosol particles at various distances we did some tests using an atomizer and 4 particle counters. We created an imitation … More
All MERV 8 Air Filters are not Created Equal – Performance Varies Greatly by Particle Size
Different MERV 8 Filters do not perform in the same way on all particle size ranges. Pleated filters have far higher efficiency on medium sized and small sized particles than polyester pads or ring panels. The ASHRAE 52.2 test method is designed to measure the fractional efficiency of a filter by particle size. One would … More
Are Air Filter Tests Representative of Indoor Particle Counts?
A great deal of effort has been expended analyzing filter test results and procedures. Are these results consistent with indoor particle counts? The ASHRAE 52.2 filter tests are designed to provide a measure of the efficiency of filters by particle size. While the MERV numbers determined by the tests give an indication of how a … More
The Effect of Particle Removal Effectiveness on Particle Levels in an Office Environment
Particle removal effectiveness is a function of filter efficiency and the air exchanges per hour but also of outdoor to indoor particle transfer, particle size and indoor activity. The purpose of this paper is to analyze the effect of air cleaning on particle counts in an office environment attached to a manufacturing facility. A 10′ … More
Children in Neighborhoods Near Highways and Railroad Intersections at Risk for Asthma
A study by Mayo Clinic shows that children living near traffic intersections at greater risk of developing asthma. Mayo Clinic researchers recently released data showing children who lived near major highway or railroad intersections have a higher risk of developing asthma. The researchers used this study to show how neighborhood environment is a risk factor … More
Study of Particle Counts in School with Mechanical Ventilation Produces Surprising Results
This study shows that a school with mechanical ventilation and a variable volume make-up air system using MERV 8 pleated filters has significant reductions in small particles but lower than expected reductions in particles in the 3 to 10 micrometer range. Health professionals often recommend that asthmatics and others with respiratory diseases stay indoors during … More
How to Use Proper Filtration and Differential Pressure to Help Control Contamination During Health Care Facility Construction
Between July and September of 1994 technicians in the clinical microbiology laboratory of Wilford Hall Medical Center at Lackland Air Force Base in Texas found Aspergillus niger in 17 clinical samples submitted for 15 patients at the hospital. This caused a great deal of consternation for two reasons: 1. The incidence of Aspergillus niger … More