Comparison of MERV 16 and HEPA filters for cab filtration of underground mining equipment

Abstract

Significant strides have been made in optimizing the design of filtration and pressurization systems used on the enclosed cabs of mobile mining equipment to reduce respirable dust and provide the best air quality to the equipment operators. Considering all of the advances made in this area, one aspect that still needed to be evaluated was a comparison of the efficiencies of the different filters used in these systems. As high-efficiency particulate arrestance (HEPA) filters provide the highest filtering efficiency, the general assumption would be that they would also provide the greatest level of protection to workers. Researchers for the U.S. National Institute for Occupational Safety and Health (NIOSH) speculated, based upon a previous laboratory study, that filters with minimum efficiency reporting value, or MERV rating, of 16 may be a more appropriate choice than HEPA filters in most cases for the mining industry. A study was therefore performed comparing HEPA and MERV 16 filters on two kinds of underground limestone mining equipment, a roof bolter and a face drill, to evaluate this theory. Testing showed that, at the 95-percent confidence level, there was no statistical difference between the efficiencies of the two types of filters on the two kinds of mining equipment. As the MERV 16 filters were less restrictive, provided greater airflow and cab pressurization, cost less and required less-frequent replacement than the HEPA filters, the MERV 16 filters were concluded to be the optimal choice for both the roof bolter and the face drill in this comparative-analysis case study. Another key finding of this study is the substantial improvement in the effectiveness of filtration and pressurization systems when using a final filter design.

Health hazard evaluation report: evaluation of erionite and silica exposure during forestry activities.

“…We observed accumulated dust inside the cab. Recent NIOSH studies have shown that an effective vehicle cab filtration system includes both a powered and pressurized air intake as well as filtered circulation air to reduce respirable dust [Cecala et al 2012;Organiscak et al 2013;Cecala et al 2014]. The ventilation system on the Bobcat Skid Steer was not powered, and there was no change-out schedule for its air filters.…”

Design, testing, and modeling of environmental enclosures for controlling worker exposure to airborne contaminants.

“…This study was conducted on enclosed cabs on both an underground face drill and a roof bolter using particle counting test methods between shifts in order to benchmark protection factor performance under consistent operating procedures. Airflow and cab pressure measurements made on these cabs during this long-term study, including several other filter combinations tested, showed that multiple leakages around the filters in the HVAC system had a noticeable impact on the overall cab's PF performance, and that these additional leakages could be incorporated into mathematical modeling of these filtration systems [Cecala et al 2016].…”

“…The performance of this cab filtration system design was further studied in the field on several pieces of underground mining equipment. Underground dust and diesel field sampling results during a seven-month field study showed inconsistent cab PFs among production shifts because of unpredictable equipment operator practices, such as the frequency and duration of opening the cab door and the variability in HVAC system operation [Cecala et al 2012;Noll et al 2014a]. Particle counting and HVAC airflow measurements made on these cabs in ambient air outside the mine between production shifts provided a better quantification or benchmarking of their optimum long-term PF performance under consistent near steady state cab testing conditions, termed "static testing" [Cecala et al 2012;Organiscak et al 2013].…”

“…Underground dust and diesel field sampling results during a seven-month field study showed inconsistent cab PFs among production shifts because of unpredictable equipment operator practices, such as the frequency and duration of opening the cab door and the variability in HVAC system operation [Cecala et al 2012;Noll et al 2014a]. Particle counting and HVAC airflow measurements made on these cabs in ambient air outside the mine between production shifts provided a better quantification or benchmarking of their optimum long-term PF performance under consistent near steady state cab testing conditions, termed "static testing" [Cecala et al 2012;Organiscak et al 2013]. Mathematical modeling of this three-filter cab filtration system using node analysis techniques was validated by the particle counting PF field test results, thereby demonstrating the model's usefulness as a filtration system design tool [Organiscak et al 2014].…”

“…A long-term HEPA and MERV 16 filter comparative study showed no overall significant difference between these filters [Cecala et al 2016]. This study was conducted on enclosed cabs on both an underground face drill and a roof bolter using particle counting test methods between shifts in order to benchmark protection factor performance under consistent operating procedures.…”