Medical Air Solutions,
Inc.
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Elements of a Negative Pressure Infectious Isolation Room Architecturally, an isolation room should meet all the detailed requirements for a single patient room, including a dedicated adjacent bathroom. To increase the effectiveness of negative pressure, the architectural elements should ensure that the isolation room suite is sealed, except for a half-inch high air gap under the door. If space and budget permit, an anteroom should be provided between the negative pressure isolation room and the corridor. This will help prevent infectious particles in the isolation room from escaping to the corridor. When an isolation room door is open, negative pressure is immediately lost. If there is an anteroom that is negative to the corridor, then the overall integrity of the suite is maintained. The anteroom provides an "air lock" between the isolation room and the rest of the facility. The location of the proposed isolation room should also be considered: areas prone to strong drafts, such as those near elevator banks or doorways, should be avoided if possible. Isolation room doors should be equipped with self-closing devices. It should be sized to accommodate the patient, but should not be oversized. A 15' x 15' to 20' x 20' room is usually sufficient for an infectious isolation room. See the Francis J. Curry document in the Reference section of this site for specifics on the "Design, Assessment and Upgrading" of infectious isolation rooms. False ceilings should be avoided whenever possible. If this is not possible, remember to include the area above the false ceiling when calculating the room volume. Walls above the false ceiling must be finished to the hard ceiling. (Note: MAS can provide sealed false ceilings to ensure any area between it and the hard ceiling remain isolated from the room proper.) Windows must be sealed so that they may not be opened by patients or staff. The intra-room airflow dynamics of the room is a critical aspect that should be considered when designing or renovating a room. The flow should be from the entrance/egress or a point beyond the foot area of the patient towards the patient's head. The exhaust should be as close to the patient's head as is physically possible. The bathroom should have it's own exhaust with only one entrance/egress. The exhaust from this room should not be included in the overall calculation of exhaust volume from the room. The bathroom should have a dedicated exhaust. Infectious Isolation rooms must have a permanent monitoring device that provides a quantitative reading. The device shall have local audible and visual alarming to alert staff to any problem with the room's pressure.
A negative pressure infectious isolation room must have more air exhausted than air supplied to achieve negative pressure. The minimum air supply to air exhaust should be a minimum of 100 CFM to more than the supply to obtain -0.005 W.C. (water column) provided the room is properly sealed. This result may not be achieved if there is leakage into the room through various orifices or openings. If a false ceiling is in place, care must be given to ensure that any leaks be plugged above the false ceiling. HVAC air diffusers are active devices that should be sized to give a throw that moves the air rapidly (30-40 fpm) toward the patient. The diffuser should be sized so that the throw is sufficient but not so large that the velocity is reduced. The use of built-in baffles or louvers to direct the air flow assists this end. Keep in mind that a fifty (50) percent safety factor should be calculated into the supply air diffuser design. This is to ensure that if more supply air is needed, it will be available. It should be noted that most healthcare institutions' exhaust/HVAC return systems were not designed to create the negative pressure that is recommended for current isolation room standards and guidelines. A dedicated air purification system (APS) is usually the solution for this shortcoming. Exhaust grilles are passive devices even if they are part of a modular air purification system. (More information will be given on exhaust equipment in the section "Exhaust Equipment") They collect air in a hemispheric 360 degree circle at the face of the grille. They should be positioned as close to the patient's head as is possible. The formula for room volume is: (Room Width) x (Room Length) x (Room Height) = Room Volume The formula used to achieve the desired ACH is as follows:
The minimum ACH for infectious isolation rooms is 12 ACH with 15 ACH being preferred. A note for the Emergency Room personnel: There are specific rooms, including the waiting room, that must now meet JCAHO standards. Review the new JCAHO "Environment of Care" standards to review what you have to do to upgrade your waiting rooms, treatment rooms, triage and other rooms in the ER area on the next major renovation.
Prefilters are required on all exhaust from infectious isolation rooms or their equivalent in all healthcare institutions. Spun fiberglass filters are prohibited due to their micro-fracturing during any type of movement or vibration. The micro-fractured fibrous fiberglass material could cause respiratory problems for some people. Only paper type prefilters or better should be used in a medical application. MAS only specifies pleated paper filters with a anti-microbial coating in our equipment. Activated Carbon filters are efficient in removing odors and volatile organic compounds (VOC). They can be utilized in areas where strong odors or chemical compounds are common. HEPA filters are the only recognized method of removing particulates and pathogens from airstreams (OSHA, JCAHO, CDC, NIOSH, et. al.). For negative pressure infectious isolation rooms this is the air purification method required by OSHA and JCAHO if you are returning the air to the HVAC system. Ultraviolet Germicidal Irradiation (UVGI) is another method of pathogen control and will be discussed later. If you are exhausting directly to the outdoors and you are not required to use HEPA filtration, but, the exhaust must be directed upward and not be within 25' of a building intake source or outdoor pedestrian area. If you are exhausting into facility air return ducting or to the outside near a building intake or populated area then you need to utilize these filters. All exhaust ducting from infectious isolation rooms must be labeled by law. This includes those areas that are identified as negative pressure rooms in CPL 2.106. If you go on the Internet you'll see all kinds of information about HEPA filters. Companies that sell air purification products that do not use HEPA filters usually are either not well educated as to what a HEPA actually is or they take information out of context when describing it. Sometimes it would appear that they simply do not tell the truth, period. The majority of sites also claim that a HEPA filter will not filter out viruses because a HEPA is 99.97% efficient at 0.3 microns and viruses are usually smaller than 0.3 microns. Viruses are usually less that 0.3 microns, but a true HEPA is extremely efficient at removing them from the air stream. In fact, a HEPA is virtually 100% efficient in removing any particle down to 0.001 microns. No government agency sets filter efficiency standards the filter companies do, but, thats another topic. The exception is with HEPA filters. The Atomic Energy Commission (AEC - now the Nuclear Regulatory Commission) needed to know what the worst case particulate flow-through was for radioactive iodine particles in HEPA filters. This new type of filter was to be used in the production of atomic bombs and these particles could contaminate workers. The AEC the set a "standard" (in 1943) that remains in effect today. True HEPA filters are 99.97% efficient at 0.3 microns. They are virtually 100% efficient at filtering out larger particles and smaller particles (down to 0.001 microns). Some points to remember:
What is a HEPA filter? HEPA Filters are generally constructed of a 0.013 inch thick glass fiber material that is bonded at the molecular level. Required minimum HEPA standards include 99.97% capture of 0.3 micrometer diameter DOP aerosol particles. A True HEPA's DOP rated efficiency (which is 99.97% @ 0.3 microns) is the MINIMUM STARTING efficiency. The actual operating efficiency is higher for all particle sizes (0.001 micron and up). The usual standard for measuring air cleaner efficiency (and for healthcare purposes) is 0.3 microns, which is the cleanroom standard DOP test (Mil-Std 282 Dioctylphthalate test, or the Potassium Chloride [KCL] test). So a "true HEPA" filter has the highest proven efficiency of 99.97% at 0.3 microns by this cleanroom test. The efficiency of any non-HEPA air cleaner is very much lower anywhere from 5% to 60% by the DOP test at 0.3 microns. Because all non-HEPA efficiencies drop with usage, their real operating efficiencies are even lower - probably between 1% to 15% within hours or days for portables. HEPA filters are far more efficient for air cleaning than other types of filtration systems. Interesting Statistics and Comparisons Where do particles come from?
Whats a Micron? 1 micron = 1/1,000,000 of a meterExamples of some common air contaminants and their size in microns:
The information in this description has been derived from various manufacturers, educational institutions and U. S. Government agencies.
UVGI (Ultraviolet - C Irradiation) Ultraviolet Germicidal Irradiation (UVGI) is a secondary method of removing airborne pathogens from the air stream. It cannot be used in place of HEPA filtration. It may be added as an adjunct to HEPA filtration. Provided that the UVGI is specified correctly, this extra measure can ensure that ALL pathogenic material is eradicated as it is collected on the HEPA filter. MAS quotes most air purification equipment with this option installed. It is important to keep in mind that UVGI is NOT a substitute for HEPA filters. UVGI offers a second line of defense against airborne pathogens but all (OSHA, JCAHO, CDC, NIOSH, etc) agencies consider the HEPA filter as the primary defense against airborne pathogens. Upper room UVGI is also used in areas where the threat of airborne pathogens may be present. Examples are the Emergency Waiting Room and the Surgical Suite. The UVGI are located near the ceiling and irradiate the upper 12 inches of the room, creating an area of lethality for microbes (Tb, SARS, etc.). Pathogens will rise with the warm air into the area of irradiation an this will eliminate many of the pathogens that may be present. Humans should not be exposed directly to UVGI, which is designated as UV-C, as this will cause skin and eye irritation. The room units should have the UV-C lamps housed in recessed troffers to prevent any exposure. UVGI may also be installed in close proximity to heating and cooling coils in air handling units. The UV-C will keep mold, mildew and pathogens from forming colonies on the coils. The added benefit of vastly increased heat transfer of the coils gives a cost benefit of up to 25% in energy savings.
Air Purification Systems and Devices Designed and modular Air Purification Systems (APS) should be designed so that the filtration aspect of the system keeps the filters totally sealed to prevent leakage and "blow-by". Here are two (2) methods of designing air purification systems for infectious isolation rooms. House systems and modular systems. House systems rely on the building's supply and exhaust systems to provide supply air and exhaust capability to establish an infectious isolation room. With systems that are balanced or programmed correctly, (Johnson Controls MetaSys, etc.) this can be effective. Unfortunately, the vagaries of computer failures and added loading to an air handling unit, may reduce the effectiveness of this type of system. Provided that power is maintained, a singular or multiple air purification systems (APS) in a healthcare institution would be impervious to these type of problems. A room where a patient admitted to a hospital's infectious isolation room would have no problem in maintaining the patient's healthy environment provided a continuous power source was supplied. The big economic factor is to get the most "bang for the buck". For new construction, most hospitals will "design in" infectious isolation rooms and surgical suites, essentially, "reinventing the wheel" for each room. Utilizing pre-engineered modular units is vastly more efficient. You are NOT re-inventing the wheel each time you construct, upgrade or renovate a room. Modular systems can be quite cost effective in this application and can be set up to initiate their own pre-programmed objectives.
This is required by JCAHO as of 1/1/03. All Infectious Isolation rooms and Surgical Suites that have had a major renovation or are of new construction, MUST have a continuous monitoring devices installed for each room. The new requirements state that the room's pressure be monitored 24/7. They should also locally alarm both audibly and visually so that personnel can become immediately aware of and correct any problems that may occur. MAS provides a monitor that performs these functions. They also have added features for providing communications capabilities with most house computer systems (Johnson Controls, Siemens, et. al.) The also have control functions that can ramp APS units up or down based on room pressure or they can simply switch the unit to high speed if the equipment has only a low and high speed setting.
Grilles and Diffusers and Ducting Air diffusers in infectious isolation rooms should be sized to allow airflow in the required amount plus fifty (50) per cent as a safety factor. The supply diffuser should be the louvered blade type, rather than the perforated face type. The diffuser neck size and blow pattern should be selected so that air is directed to all parts of the room. The diffuser should be located where airflow is not obstructed by items such as surface-mounted light fixtures or a suspended television set. Exhaust grilles should be sized to exhaust the needed amount of air plus fifty (50) percent as a safety factor. The primary exhaust should be as near to the patient's head as possible. The bathroom should also have a dedicated exhaust. The exhaust fan discharge should be located and designed to minimize the possibility that this air is inhaled by people who are outdoors or inside the building. Exhaust air should be directed away from occupied areas (i.e., walkways) or openings into the building (i.e., windows or outside air intakes). To promote dilution, the fan discharge should be directed vertically upward at a speed of at least 2000 feet per minute (FPM). The discharge location should be at least 25 feet away from public areas or openings into a building. Ducting should be well sealed at the joints to prevent leakage into the isolation room and any other areas where the duct passes through. We recommend that grilles, diffusers and exhaust ducting within the isolation room be constructed of stainless steel for ease of cleaning and durability.
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