A-J Manufacturing provides the highest quality HEPA and ULPA Filters currently available as options in our stainless steel laminar flow and radial flow diffusers, or any combination grille, plaster frame, and plenum models in hinged or non-hinged models. Typical applications include hospitals, semiconductor manufacturing, disk drive and compact disk manufacturing, food processing, pharmaceutical production and aerospace manufacturing.
Our standard filters incorporate an anodized aluminum Gel Seal frame that makes with a specially constructed frame on our diffusers to provide a leak-tight connection. The filters also utilize a separatorless 2? (51) deep media pack as standard and we provide a test port integral with every filter. The test port is used to measure filter pressure drop, perform leakage (scan) tests or to adjust balancing dampers in the diffuser neck.
All filters are UL 900 Class I Listed and Factory Mutual Approved. All filters are individually scan tested per Section 6.2 of IEST-RP-CC034.1. Filters are packaged independently from the diffuser for final installation of the filter in the field (by others). ULPA filters are assembled and tested in a cleanroom environment before being sealed in a polybag.
Filter Selection & Applications
Most people are commonly aware of the extremely high filtration offered by these filters, however proper application requires an understanding of the test methods and ratings.
HEPA filters have 99.99% minimum removal efficiency on 0.3 micrometer particle size.
ULPA filters have 99.995% minimum removal efficiency on 0.12 micrometer particle size.
It is very important to realize that the testing is done with an aerosol of specially constructed man-made spheres, not with biological or irregular shaped particles. This is necessary to provide a repeatable test and ensure manufacturing quality, however, depending on the applications and conditions involved, actual efficiency may me somewhat lower. Recent studies with biological particles indicate they may migrate of their own accord through the filters over time. This can be explained due to the fact that some bacteria have flagella which enable movement and possible detachment from filter fibers; also, some bacteria are surrounded by gelatinous surfaces (slime) which may reduce filtration efficiency. Some fungal spores and bacteria will grow in the presence of moisture and could grow through the filter element over time.
Another important thing to note about filters is their most penetrating particle size range. The filtration efficiency of filters follows a specific nonlinear curve. Classification of HEPA filters is their efficiency at a particular diameter of particle (0.3 micrometers and larger). Generally, a smaller diameter particle, say 0.2 micrometers, will have a slightly lower filtration efficiency which could also depend on air velocity. Many of the pathogens responsible for nosocomial infections have particles in this size range. It is important to note that many pathogens that are attached to larger particles or are found in clumps will break apart upon contact with the filter fibres. Therefore, it is recommended that actual particle size be used to determine a conservative fitltration efficiency requirement. Also, the testing is performed at 100 fpm (0.51 m/s) velocity on the net media face area. Table 4 gives the net media face area of our standard filters and the recommended airflows. The filters have been shown to maintain their ratings at up to 150 fpm (0.76m/s) velocity and 2? (500 Pa) pressure drop and this is the maximum shown in the chart and our performance data. Once again exceeding thses criteria could reduce filter efficiency. Also, particles are typically not evenly deposited on the filter and there could be localized areas on the filter that will exceed the maximum velocity as the filter gets dirtier.
Disinfection & Sterilization
The subject of disinfection and sterilization in healthcare facilities (like most healthcare related issues) is extremely controversial. Most authorities do not agree on the type, frequency or effectiveness of the various methods and chemicals. The result is that many hospitals use many different methods and new research and product developments continue to influence actual practices. The evolving trend seems to be towards stricter controls and higher levels of disinfection. Newer construction guidelines focus on surfaces that are resistant to harsh cleaners, have no cracks or crevices and are easier to clean such as monolithic ceilings in operating rooms, etc. The sanitation requirements in the operating room are the most severe as they are aimed at total asepsis. This requires the use of strong cleaners, usually highly alkaline soaps reinforced with synthetic detergents. In addition to meeting the regular standards of cleanliness, the general cleaning is supplemented with sanitizers, disinfectants and sterilants. These chemical formulations are functional against different levels and types of contamination. Sanitizers reduce but not necessarily eliminate microorganisms. These cleaners contain lye (caustic soda, sodium hydroxide) and alkaline hypochlorites (equivalent to bleach). Often these and other cleaning and sanitizing agents will have the alkaline salts aided by ‘quats’ (quaternary ammonium derivatives). Disinfectants go one step further than sanitizers in that they eliminate all pathogenic microorganisms, that is, they destroy infectious fungi, viruses and bacteria, but not necessarily their spores. These agents may also contain ‘quats’ such as quaternary ammonium chloride or phenolics (carbolic acid derivatives) with the addition of detergents, either soaps, surfactants or both. Some of these agents, especially in concentrated form, are in an alkaline solution and have an extremely high pH level 12.5 – 13.8 (similar to paint stripper or concentrated lye). Sterilants cap the assault on disease producing agents. They destroy all forms of microbial life and their spores. Complete sterilization of environmental surfaces is not possible or practical in health care facilities however and many sterilants are used as high level disinfectants. They include acids such as phenol (carbolic acid), citrosols (buffered citric acid), phenolic derivatives such as hexachlorophene, peracetic acid/hydrogen peroxide. On the alkaline side they include lye, terpenes, high pH germicides, glutaraldehydes. It is easy to see that most of the above chemicals will be corrosive to metals, especially those containing chlorine compounds. Most metals typically used in HVAC systems are carbon steels protected by sacrificial coatings such as zinc, zinc alloys, aluminum or aluminum sheet. Aluminum and the coatings used to protect carbon steel are amphoteric, which means that they are attacked (corroded) by alkalis and acids. Therefore any agent with a pH lower than 7 (acidic) or higher than 7 (alkaline) are corrosive to these surfaces. It is important to understand that metallic materials do not corrode evenly or uniformly.