Protecting Patients, Frontline Staff, and Caregivers with HEPA filters
The hospital and medical industry is a vast and unique industry. Due to its special characteristics, the virus and bacteria content in hospitals is relatively high, so excellent ventilation systems with Hepa filters are needed to ensure hospital air quality.
Especially the operating theatre and other high-grade clean room air cleanliness requirements are very high.
Generally, qualified hospital operating theatre purification projects or medical cleanrooms have minimum requirements for hospital air to be filtered using a combination of pre-filters with a 40% efficiency and Hepa filters with a 99.99% efficiency.
How Does a HEPA Filter Work in a Medical Environment?
It is the physical removal of airborne particles, contaminants, human hair, mold, germs, and bacteria from the air using certain unique materials to clean it.
It is to prevent internal or external pollution by living particles and control internal pollution by inanimate particles.
Hepa filter is also used in air purifiers with an activated carbon filter to remove odors, airborne contaminants, mold spores, mold, viruses, and pathogens in hospital wards or doctors’ offices.
It is also widely used in hospital operating theatres, sterile supply centers, ICUs, neonatal rooms, general protective isolation wards, burn wards, dental offices, clinics, and laminar flow wards.
Hepa filters to ensure high air quality in hospital clean rooms.
Hospital clean rooms include operating theatres, obstetrics, infant and child wards (NICU), ICU (Intensive Care Unit), burn wards and autopsy rooms, purification laboratories, artificial dialysis rooms, specimen rooms, etc. Clean air quality has a direct and essential relationship with medical quality.
The most widely used clean environment in hospitals is the operating theatre which requires the highest grade of clean air.
This modern operating theatre uses clean air technology instead of the old-fashioned ultraviolet light and other means of contamination control throughout the process.
In a clean operating room, infection rates can be reduced by more than ten times.
The efficient and safe operating theatre Hepa air purification system ensures a sterile operating theatre environment that can meet the high level of sterility required for procedures such as excision, transplantation, and replacement.
Features of medical grade Hepa filters
Hospitals require high-efficiency particulate air filters with the following points: robustness, high efficiency, ease of handling, low resistance, and stable filtration efficiency.
1. Medical-grade HEPA filters can block airborne contaminants such as dust, PM2.5, microscopic allergens, bacteria, viruses, and molds with a size of approximately 0.01-10 microns. 1 micron (um) = 0.0001 cm (cm)
2. Medical-grade HEPA filter is made up of intricately shaped fibers.
The fibers can block tiny dust particles (0.1-0.3um) with a filtration efficiency of over 99.97%.
The fibers are also attracted to tiny dust particles, sticking to the fibers and preventing them from passing through.
3. Medical grade HEPA filters vary in effectiveness for different particle sizes, filtering most particles from 0.1 to 0.3um, while larger particles are filtered at close to 100%.
4. Medical-grade HEPA filters become more effective as they are used over time until wholly blocked.
This phenomenon is due to the accumulation of contaminant particles, which causes the gaps in the fibers to become smaller and smaller, making the structure of the filter more and more complex.
As a result, new contaminant particles do not only stick to the fibers but also to the existing ones.
Maintenance of purification and ventilation systems
Hepa air purification aims to provide clean and germ-free air in the room.
Major working defects have occurred in the filtration equipment or decontamination systems from the many clean operating theatres built.
Regular maintenance of ventilation and decontamination systems is essential.
1. We need to set up an engineering maintenance department with professional skills, organize professional training in clean technology, carry out work in a standardized manner, and keep maintenance records seriously and strictly. The maintenance records should be appropriately maintained for inspection.
2. Regular inspection and maintenance of clean air conditioning units. Once a month, check and clean the interior, especially for the heat exchangers, and flush them with high-pressure water.
3. Strengthen the inspection and maintenance of ventilation units. Check once daily to keep the interior clean; replace the primary air filter every 1 to 2 months; replace the medium efficiency air filter every three months; replace the Hepa filter every year.
4. The HEPA filter should be checked every six months to ensure cleanliness meets the requirements. It should be replaced when its resistance exceeds two times the design’s initial resistance or when it has been used for more than 1-2 years.
5. The exhaust air unit’s medium efficiency/HEPA filter is replaced annually. In the case of unique contaminated surgery, the filters must be replaced for each surgery, and the replacement filters must be transported out in a sealed container and disposed of by incineration.
6. Suspended air supply ceilings should be inspected once a month, and the internal surfaces of the diffuser panels should be cleaned with medical alcohol (except for leak-proof roofs).
7. The return air outlet filter should be checked regularly and replaced once a year. If unique contamination surgery is done, the filter must be substituted for each surgery case, the filter should be sealed out and incinerated, and the internal and external surfaces of the return air outlet should be wiped with a disinfectant solution.
Particular indicators for monitoring hospital cleanrooms
These indicators reflect the impact and working condition of the Hepa filtration system on the hospital clean room and give a good idea of how the HEPA filter works.
Suspended Bacteria Concentration: This is primarily used to dynamically monitor the actual bacterial concentration in the operating state of a procedure and to detect and predict the risk of infection in specific procedures under a combination of factors.
Dust concentration: mainly used to monitor the level of static cleanliness and to locate the number of air particles greater than or equal to 0.5µm and the number of dust particles greater than or equal to 5µm.
Differential pressure: The primary purpose is to monitor the normal differential pressure in each area of the clean surgery department to prevent incorrect airflow directions.
Wind speed and volume: The specification requires that the cross-sectional wind speed be controlled within 0.25 to 0.3m/s on the working surface of the local operating theatre.
Cleanliness requirements for hospital operating theatres
The cleanliness of each clean room in a hospital varies according to the requirements of its different areas (e.g., operating theatres, sterile preparation rooms, anesthetic rooms, and surrounding clean areas).
Different levels of laminar flow operating theatres have different standards of air cleanliness.
For example, the US Federal Cleanliness Standard Class 1000 is the number of dust particles per cubic foot of air ≥0.5μm, ≤1000, or ≤35 per liter of air, while the standard for Class 10000 laminar flow operating rooms is the number of dust particles per cubic foot of air ≥0.5μm, ≤10000 or ≤350 per liter of air. And so on.
Ventilation system for sterile operating theatres
The main objectives of operating theatre ventilation are to remove exhaust gases from the workrooms, to ensure the necessary amount of fresh air, to remove dust and micro-organisms, and to maintain the essential positive pressure in the room.
The following two types of ventilation are available to meet the ventilation requirements of the operating theatre.
- Mechanical air supply and mechanical exhaust: this type of ventilation can control the number of air changes, the volume of air changes, and the pressure in the room, and it has a better ventilation effect.
- Mechanical air supply and natural exhaust air： the volume and number of air changes in this ventilation method are limited, and the ventilation effect could not be better than the former.
The number of dust particles and biological particles in the air mainly distinguishes the cleanliness level of an operating theatre.
Purification technology controls cleanliness through positive pressure purified airflow and Hepa filter to achieve sterility in hospital operating theatres.
Types of Hepa medical purification technology
Depending on the air delivery method, Hepa medical purification technology can be divided into multi-direction and laminar flow systems.
Multi-direction flow system
The multi-direction flow system’s air supply and Hepa filter are set in the ceiling, and the return air is placed on both sides of the lower part of one wall. Filter and air treatment are relatively simple, convenient to expand, and cheap.
However, the number of air changes is small, generally 10 to 50 times/h. It is easy to produce a vortex, and polluting particles may be suspended and circulated in the indoor vortex area, forming a polluted airflow and reducing the indoor purification degree.
It only applies to the clean room of NASA standard 10 000 ~ 1000 000 level.
Laminar flow systems
The laminar flow system uses an evenly distributed and appropriately flowing airflow to carry particles and dust out of the operating theatre through the return air outlet without creating eddies. There is no floating dust, and the degree of purification increases with the number of air changes.
It is suitable for operating theatres of class 100 in the NASA standard.
However, the Hepa filters are densely replaced more often, and the cost is higher.
Hepa air purification system in medical
Hepa air filtration is the most effective, safe, economical, and convenient means of germ removal.
Using suitable air filters ensures that the required dust and bacteria concentrations are achieved in clean operating rooms at a reasonable cost.
Three-stage filtration
Usually, the entire clean operating room purification and air conditioning system has three levels of air filtration.
The first stage of air filtration should be set at the fresh air inlet, the second stage at the positive pressure section of the system, and the third stage at the end of the air purification system.
A three-stage filtration system is also required for a separate air purification system, with at least a Hepa air filter as the final stage.
The excellent performance of the end HEPA filters guarantees a sterile indoor environment. At the same time, a good configuration of the filtration system can extend the service life of the end HEPA filter and make the resistance of the three-stage filtration system grow smoothly.
Although it has been proven as early as the 1980s that filters with a colorimetric efficiency of 90% to 95% (equivalent to H12 efficiency filters) can filter out 99.9% of all bacteria in hospitals, the latest revisions to hospital ventilation filtration standards in various countries have generally increased the filtration efficiency requirements.
The standard emphasizes the need for Hepa air filters in clean operating theatres. Since the sterile operating room is a safeguard system, electrostatic cleaners should not be installed at the end of the air supply.
3-stage filtration as an integrated system
The concept of three-stage filtration is complete, and the filtration system must be configured appropriately.
In order to achieve the overall effectiveness of a Hepa filtration system, the selection and location of each filter stage should be considered.
Neglecting a particular part of the process or a mismatched filter setting at one level can result in unreasonable replacement periods for the three-stage air filters, resulting in problems such as poor overall filtration performance.
Note of choosing HEPA filter for medical
Although the primary performance of the terminal medical grade HEPA filter for clean operating rooms is filtration, its other properties also affect the sterility of the room environment. They need to be carefully selected and compared with regular HEPA filters.
Under normal circumstances, Hepa filters do not breed bacteria. In order to eliminate the possibility of bacteria breeding, the material used in the filter should be water-repellent, and organic materials should not be used, such as air filters with plywood or wood panels in the frame.
If the end filtration device uses a deep pleat hepa filter, products with a kraft paper or coated paper separator should be excluded, and an aluminum separator is preferable.
If the end filtration device uses a mini pleat Hepa filter, using a product with melt glue as a separator is advisable.
In addition, the use cycle of the filter should be a manageable length.
Set a filter for the return air outlet.
Attention should be paid to installing a filter at the return air outlet and, if the room pressure permits, setting a medium-efficiency filter at the return air outlet.
The return air may contain more hair and textile fibers due to the operation of the personnel in the clean operating room and the pre-and post-operative cleaning work.
These fibers are particularly likely to be deposited on the ducts through the return airlines, causing dust to accumulate and breed bacteria.
Or they were deposited on the coil, affecting heat transfer efficiency, or even blockage, reducing airflow.
Establishing positive pressure with an air filter at the return air outlet is also easier.
