HEPA filter with MERV 17 rating traps 99.97 percent of air contaminants

Sandeep Vasant, National Sales and Business Development Head – India Hyperscale Data Centre, FläktGroup India, says that in air handling units, MERV 5 and MERV 8 filters could be installed ahead of HEPA filters as a 2 step filtration process.

 

Air filters in HVAC system 

In a HVAC system, the air filter is implemented as a standard filtration component. The HVAC systems vary in size from a smaller capacity of split type air-conditioners used at home/ workspace, to larger capacity of air handling units connected to a centralised air conditioning system like chillers. The larger capacity AHUs are used in applications such as hotels, malls, multi-tenant buildings, commercial buildings, industries, etc. Primarily, the air filters’ function is to filter dust, bacteria, virus, pollen and other micro and small particles from the air which we breathe. Filters also protect the external and internal components such as fans, coil, and compressors on the HVAC systems by reducing airborne contaminants to accumulate.

 

Studies indicate that people spend close to 80 percent of their time indoors – inside residences, offices or other commercial buildings. Hence, filters constitute a very crucial part of the HVAC systems. They are essential for a healthy indoor climate providing clean and fresh air quality to protect people’s health. As per sources, the future of the Air Filters market is projected to grow from USD 13.75 Billion in 2022 to USD 22.15 Billion in 2028 at a CAGR of 7.1% from the 2022 ~ 2028 period.

 

The latest trend for the filtration process is innovation.Filters used in HVAC systems are available in the grade and range of MERV 4 up to MERV 16 and HEPA Filters. A filter receives a MERV (minimum efficiency reporting value) rating as determined by the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE). On an average, facilities are limited to a MERV 8 or MERV 9 filter type. Essentially, a HEPA filter is the ultimate solution among the air filters range. All HEPA filters have a rating of a MERV 17 or higher. A HEPA filter with a MERV 17 rating will trap 99.97 percent of air particles. These particles are 0.3-1.0 micron in size. Hence the HEPA filters in most of the air filtration units are certified to capture almost 96 percent of the Covid causing germs

 

In air handling units, MERV 5 and MERV 8 filters could be installed ahead of HEPA filters as a 2 steps filtration process. It reduces the dust load and also helps increase the life of the HEPA Filters. Two steps filtration is recommended as follows: 

• Min. MERV 9 (M5) or if possible MERV 13 (F7) in the 1st stage 
• Min. MERV 13 (F7) or if possible MERV 15 (F9) in the 2nd stage 
• Min. MERV 13 (F7) if only one filter step is used.

 

The indoor contaminants also include gaseous contaminants such as VoC, NOxSox, Ammonia, Formaldehyde etc. Hence, Filter Media with activated carbon and activated alumina will also help to remove these contaminants.It has been noticed that a ePTFE media is superior to a glass fiber for HEPA filters, as efficiency of ePTFE is 0.07 microns as against 0.13 microns of glass fiber. It also offers 50 percent lower pressure drop and 8 times higher strength and higher dust holding capacity. This improves the overall efficiency of the HVAC system .

 

Apart from the above innovation methods, during the working cycle of the HVAC system, ‘Filters common best practise’ mentioned below should be followed. 

• Testing of Filter as per standards 
• Monitor and measure the energy consumption attributed from filters 
• Measurement of IAQ 
• Regular cleaning, washing or even revamp of the filter yearly / quarterly/monthly based on the application and dust fixation.

 

The basis of the right filter selection should be referred to ASHRAE 52.2. And, to maintain the right Indoor Air Quality, the reference should be made to REHVA Covid-19 guidance document, April 3, 2020, ISHRAE Covid-19 April 13, 2020 and ASHRAE 62 norms.

 

Air cleaners 

The air cleaner, a mobile air purification device circulates air inside the room to remove contaminants thus improving indoor air quality. They are either small stand-alone units or larger units placed on the floor of a room with one or two filtration units integrated. The air cleaners are equipped with either F7 filter or HEPA Filter to tackle the air contaminants and microbial particles such as bacteria, yeasts, viruses and the Covid virus. The reports indicate the global air cleaner is expected to expand at a compound annual growth rate (CAGR) of 10 percent from 2021 to 2028. According to a study conducted by the University of Helsinki, Finland, it was proven that either a filtration unit or an air purifier should draw enough air consistently to reduce the number of particles carrying the virus that persist in the air. Therefore, such air cleaners help reduce airborne contaminants in a building or any closed environment applications.

 

Utility of air curtains for storage and warehouses

 Air curtain-protected doorways have been proven to save total building energy usage by a factor of 0.3-2.2 percent according to Wang’s studies. This illustrates they are equal or more effective at separating outdoor and indoor environments, regardless of the cycles and door opening styles. Air curtains blow a controlled stream of air across an opening to the other side to create an air seal. This seal separates different environments while allowing a smooth, uninterrupted flow of traffic and unobstructed vision through the opening. This helps to maintain the required temperature in such storage and warehouse. The global Air Curtain market is valued at USD 428.9 million in 2019. The market size will reach USD 528.7 million by the end of 2026, growing at a CAGR of 3.0 percent during 2021-2026.

 

Implementing UVGI air purification technology 

As of now, good indoor air quality is of prime significance to ensure maximum productivity by circulating good air. Today, the customers are implementing the UVGI air purification technology in the existing buildings equipment. They are even asking for UVGI as part of the equipment schedule for new buildings as well.

 

UVGI, the Ultra-Violet Germicidal Irradiation disinfectant device emits an ultraviolet light. It makes use of shortwave Ultraviolet – C (UVC) energy wavelengths of 280-100 (nm) to inactivate microorganisms. The UV light damages the structure of the nucleic acids and proteins at the molecular level, making them incapable of reproducing. The optimal wavelength required for inactivating microorganisms is 253.7nm (CH17, HVAC Systems & Euip , ASHRAE). Two types of UVGI Devices that perform disinfection within an indoor environment are available i.e., Upper -Room (Upper Air) UVGI and In-Duct UVGI. Each of these can be implemented depending upon user application and needs.