October 2016

medical room with equipment

Filters for Isolation Rooms and Gaseous Pollutants

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For isolation rooms in hospitals, the main goal is to keep airborne infectious diseases such as tuberculosis from entering the atmosphere. To accomplish that, the air from hospital isolation rooms is filtered on the exhaust side as well as on the incoming side, using a sophisticated exhaust fan system on the ceiling where the air has to go through a minimum of two stages: a pre-filter stage and a high efficiency particulate air (HEPA) stage.

Both particulate and gaseous pollutants cannot be removed by a single air filter. Particulate matter is removed by High Efficiency Particulate Air filters (HEPA). The HEPA filter is the most effective filter in removing 99.97% particulates 0.3 micron or larger.

Gaseous pollutants such as sulfur dioxide, carbon monoxide and nitrogen oxides are removed by using activated carbon filters. Carbon filters such as the carbon v4 bank filter which are used in commercial and industrial buildings, are designed to trap smoke, odors, chemicals and gases from the air. Activated Carbon filters are often used in conjunction with a HEPA filters in public commercial settings such as hospitals, museums and airports to remove the larger air particulates.

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rooftop hvac system and other equipment

Low Pressure Drop Air Filters

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The low-pressure drop is what equates to the amount of electricity it takes to push the air through the filter. The more electricity or power it takes to push the air through the filter, the higher the pressure drop. Energy is very important in regards to filters because the lower the pressure drop, the less amount of power it’s going to take to push the air through the filter. EFS conducts as much research and development as possible in order to get the pressure drop of high efficiency air filters as low as possible while still being able to effectively filter the air.

When selecting low pressure drop air filters as an upgrade to the HVAC system, decision makers should evaluate total system costs. In addition, a life cycle cost analysis should be conducted, which takes into account initial product cost, operating cost (energy consumption), installation cost (labor), and product replacement cost. Higher efficiency filters, while typically more expensive than commonly used low-med efficiency products, are found in most HVAC systems today.

Most HVAC systems are equipped with filters designed to keep equipment components—such as coils, compressors, fans, and ductwork—clean in addition to creating a cleaner air environment. Higher efficiency air filters typically run at a higher airflow pressure drop than lower efficiency filters . Today, however, technology is emerging to increase filtration efficiency while reducing energy consumption. Although higher efficiency filters have higher initial costs, their benefits offset those costs, and pay for themselves within a year or less. Delivering cleaner air throughout the building has the additional benefit of keeping HVAC system components operating at peak energy efficiency, saving still more in energy and maintenance expenses.

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worker wearing hair net and another worker wearing hairnet and facemask

HEPA Compliant Filters

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HEPA filters are deemed compliant based on the way they are tested. They’re tested by third parties; no manufacturer can test their own filters. In the United States, there are specific labs to send filters to that are government regulated, and they have to test the filters under ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standards. These standards are constantly being worked on based on the medias that are available.

The filters themselves are regulated and tested, not the manufacturer. For HEPA-grade filters have to be tested through ASHRAE standards in addition to a DOP test. It’s the third-party that is regulated by ASHRAE standard, not the manufacturer.

By definition all HEPA filters are individually certified as to conformance with their target efficiency. The data from the testing is provided on a label on every filters stating test airflow, resistance to airflow and penetration (the inverse of efficiency). Originally HEPA filters were tested using dioctylphthalate, a known carcinogen, as prescribed in the original military testing standard authored to address HEPA filter performance.

Today, manufacturers test each HEPA filter according to methodologies as outlined in Recommended Practices (RP) as published by the Institute of Environmental Sciences and Technologies (IEST). Filters are challenged with particles of specific size and the penetration of each filter is so recorded.

The minimum level of HEPA filter performance is an efficiency of 99.97% when tested on particles 0.3 micron in size. As technology has advanced, and the need of ultra clean air in industries such as microelectronics and pharmaceutical has evolved, filters have become available that can provide a performance of 99.999995% efficiency on particles 0.12 micron is size. Because a HEPA manufacturer cannot be responsible for transportation of the filters to the user or handling and installation, many applications require additional in-place testing to ensure the installed integrity of the HEPA filter.

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