Hospitals are a vast and unique industry with very high air cleanliness requirements. Typically, the minimum requirements for hospital air are filtration using a combination of a pre-filter with an efficiency of 30% and a final filter with an efficiency of 90%.
HEPA filter filtration is not generally required, but in exceptional circumstances such as operating rooms, specific testing, and nursing areas, HEPA filtration is required.
A fair number of the projects I have completed are hospital projects, which often require HEPA filter boxes and air filters, including HEPA filters. While working with hospital builders or designers around the world, I have learned a lot about operating room air filters, and I have compiled some of the key information into this article.
1. Operating room cleanliness
Hospital clean rooms were first used in operating rooms. At first, it was only widely used in orthopedic surgeries, which took a long time and required a controlled, clean environment. The ideal level of control is to achieve Class 100 air cleanliness near the operating table. It’s typically advised to employ a high-quality HEPA filtration system that covers a space of at least 3m x 3m, encompassing both the operating table and individuals present.
Various laminar flow operating rooms adhere to distinct air cleanliness standards. For example, the US federal standard level 1000 specifies air quality with a maximum of ≤1000 dust particles measuring ≥0.5μm per cubic foot of air or ≤35 particles per liter of air.
The standard for a 10,000-level laminar flow operating room is that the dust particles ≥0.5 μm per cubic foot of air are ≤10,000 or ≤350 particles per liter. And so on.
2. What are the replacement intervals for air filters at each level?
The primary-efficiency filter is usually replaced every 2-3 months, and the medium-efficiency filter is replaced every six months. In this way, the life of the high-efficiency filter can generally be more than 2 years.
However, to protect the use of post-stage high-level filters and ensure the operation of clean rooms, many hospitals replace primary-efficiency filters every month and replace medium-efficiency and sub-efficiency filters every 3 months (or use high-efficiency filters as protection filters in the final section of the wind cabinet). This can ensure the service life of the high-efficiency particulate air filter for more than 5 years.
Moreover, because the new air filter has low resistance after replacement, the air conditioner’s load is significantly reduced, and the filter replacement cost is much less than the electricity cost required for the air conditioner’s operation. Frequent replacement of the front-stage pre-filter allows the air conditioner to operate under a low resistance load, saving money. Huge electricity bill.
Therefore, to effectively extend the service life of the high-efficiency filter, the basic method is to block dust at the primary and medium-efficiency filters.
3. Can HEPA filters be washed with water or vacuumed in hospitals or operating rooms?
The filter material of the HEPA filter is mainly composed of glass fiber paper or PP material. The filter material is generally polypropylene or other composite materials, looks like paper, and has a filtration efficiency between 90%-99.999% (0.3um).
Because the filtration precision of dust particles is relatively high, the requirements for the filter paper are relatively high and must not be damaged. If damaged, the filtering effect will be lost. Therefore, the HEPA filter cannot be washed. Do not use a vacuum cleaner to damage the filter paper structure and lose the barrier—and filtering effect.
4. How can you reduce the replacement of HEPA filters?
From my experience, you can consider the following options:
Do an excellent job maintaining the AHU’s primary and secondary efficiency filters and strictly abide by the replacement procedures of primary and secondary efficiency filters. Generally, the primary efficiency filter is replaced every 3 years, and the intermediate efficiency filter is replaced every 6 years.
Clean the fresh air ducts regularly. For example, when replacing the high-efficiency filter for the first time, you can clean the air supply duct to reduce the burden on the high-efficiency filter after replacement.
5. How often should HEPA filters be replaced in laminar flow operating rooms?
The primary function of the HEPA filter in the laminar flow operating room is to remove bacteria, viruses, particles, and other pollutants in the air to provide a clean surgical environment. The filtration efficiency of the high-efficiency filter is as high as over 99.9%, which can effectively reduce the concentration of bacteria and viruses.
Generally speaking, the service life of high-efficiency filters in laminar flow operating rooms is 1-2 years. However, in some cases, the filter may need to be replaced more frequently. For example, when the amount of surgery is large, the use time is extended, the daily cleaning and disinfection is not standardized and thorough, the surgical clothes (clothing) produce lint, the ventilation pipeline unit has not been cleaned and maintained for a long time, etc., the service life of the filter may be will be shortened.
In addition, if the filter is damaged or its performance declines (tested by professional instruments), it must be replaced in time.
6. What are the dangers of not replacing HEPA filters in time?
I think it will bring the following adverse consequences
- The air conditioning unit’s exhaust volume is insufficient, affecting the unit’s operation.
- The resistance of the HEPA filter is too large, which increases the energy required by the air conditioning unit, the unit load, and energy consumption.
- The actual compression ratio of the air conditioning unit increases, the host load increases, the electricity bill increases, the operating cost increases, and the unit life is shortened.
- The filter is blocked by dust, lint of clothing, etc., and the filtration efficiency of the filter decreases, resulting in a decrease in indoor cleanliness.
- The HEPA filter becomes a source of pollution, produces secondary pollution, is blown into the air, and may even cause pollution in the hospital.
7. How to improve the service life of HEPA filters in laminar flow operating rooms?
First, choosing a good quality filter brand like KOIN and a proper model will ensure its performance and service life.
Control the concentration of pollutants in the operating room and reduce the burden on HEPA filters.
Reasonably arrange the time and number of surgeries to avoid long-term and high-intensity use of HEPA filters.
In addition, regularly check and maintain the HEPA filter and replace it promptly if damage or performance degradation is found.
8. What conditions should be met before installing a HEPA air filter in the operating room?
Before installing the HEPA filter, the decoration and piping routes of the operating room were finished and approved.
The operating room has undergone thorough cleaning and wiping, and the purification air-conditioning system has been wiped down and subjected to continuous testing for over 12 hours.
The installation area and associated components of the HEPA filter have been thoroughly cleaned and wiped down.
The HEPA filter requires a visual inspection. The frame, filter paper, sealant, and other components should be free from damage, such as deformation, breakage, or detachment.
9. What aspects must be considered when installing HEPA filters in the operating room?
Regarding the installation of HEPA filters in operating rooms, the following aspects should be noted:
When transporting and storing high-efficiency filters, they should be positioned according to the manufacturer’s designated direction. It should be handled carefully during transportation to prevent severe vibration and collision and avoid artificial damage.
While installing, adjustments should be made appropriately according to the resistance of each HEPA filter. In unidirectional flow, the variance between the rated resistance of each filter and the average resistance of each HEPA filter from the same air outlet or air supply surface should be kept under 5%.
The sealing between the HEPA filter and the frame typically employs gaskets, negative pressure seals, gel seals, etc. It is essential to ensure that the filter frame surface, installation frame surface, and gel tank are thoroughly wiped clean.
The sealing gasket thickness should not surpass 8mm, with a compression rate ideally ranging from 25% to 30%. The joint form and material must adhere to the design specifications, ensuring no leakage occurs at the frame’s joints.
When utilizing a gel seal for the HEPA filter, it’s essential to install the tank frame horizontally, ensuring no leakage, dirt, or moisture is present within the tank.
The sealing gel’s height within the tank should be maintained at 2/3 of the tank depth, and the sealing gel’s melting point should exceed 50°C.
Last summary
The cleanliness of hospital operating rooms is usually level 100. In addition to maintaining the efficiency of the HEPA filter, daily maintenance of the operating room is also essential. For example, powdered gloves are prohibited in level 100 laminar flow operating rooms.
All cleaning work must be done with a damp cloth during the operation of the filtration system.
Before entering the operating room, all instruments and equipment should be installed and thoroughly wiped clean.
