An important approach to lowering the concentrations of indoor air contaminants including any viruses that may be in the air is to increase ventilation – the amount of outdoor air coming indoors. Ensuring proper ventilation with outside air can help reduce the concentration of airborne contaminants, including viruses, indoors.
The growing epidemic of the coronavirus COVID-19 is creating an increased attention of people to security measures.
Is the coronavirus transmitted through central ventilation?
The particle size of the virus is less than 0.1-0.14 microns. It is transmitted by airborne droplets through coughing, sneezing, etc. According to various sources the virus lives on objects and surfaces from several hours to several days. In this case the forced ventilation system is responsible for ventilating the room, supplying fresh air from the street and removing the exhaust air from the room.
Thus, it can be concluded that ventilation systems contribute to a healthier indoor environment. This is especially true for offices, shops, business centers where there is a fairly large number of people.
Therefore, it is recommended to operate the ventilation systems daily including non-working hours and at night. This reduces the likelihood of the spread of coronavirus.
If the premises do not have a forced ventilation system it is recommended to at least ventilate the room as often as possible. At least 2-3 times an hour.
The air recirculation system is not recommended to use to minimize the virus effect because part of the exhaust air flows back into the room. It can only worsen the situation and increase the likelihood of the virus spreading from one part of the room or office to other rooms and even floors.
It’s dangerous if rotary heat exchangers or recuperators are used in the ventilation system. Extracted air and supply air have direct contact through special channels where there is a possibility of a virus entering. There is a risk of transmitting the virus from the extract air to the supply air and it get back into the room again.
Using of air conditioning systems and fan coil units helps the virus spread faster. This equipment moves air around the room and they take warm air in the room, cool it and return it to the room.
Some filtration systems help fight coronavirus. Filters such as a HEPA filter and a carbon filter have an effect when used in a ventilation system to combat the virus.
The source of the virus is most likely indoors and not outdoors where we take supply air. Therefore, the use of filters is advisable at the moment only when it used in systems. And part of the air circulates inside (recirculation, air conditioning, fan coil units, etc.)
HEPA filter is a class of filters according to international standards EN 1822-1: 2009. The effectiveness of HEPA filters is evaluated by the number of particles up to 0.06 microns in size per liter of air which are thrown back into the environment after passing through the filter.
It is able to capture finer particles than coarse and fine filters. But at the same time, COVID-19 particles (0.1-0.14 microns) can penetrate in some amount depending on the filter class. Therefore, the effectiveness of this filter is in doubt especially not the highest class.
Bactericidal filters, ultraviolet lamps help to disinfect the air. At the moment there are no studies that would accurately confirm that this virus is "afraid" of such solutions. But at least this is the highest degree of protection and is widely used for increased air purification where it is required. For the most effective fight against various viruses it is recommended to maintain the temperature in the system from 60 to 77 degrees Fahrenheit.
Carbon filter is not designed to fight viruses and small particles. Coal acts as an absorber (sorbent) for harmful gases.
Summing up there are several important points:
We fully owe our comfortable stay in any room to the ventilation system. It is responsible for creating and maintaining comfortable microclimatic conditions in the enclosed spaces whether it be a residential building, work office, clinic, cafe, cinema or shopping center.
But behind such an ordinary thing today as ventilation is a long and painstaking work of qualified specialists: the installation of any ventilation system requires an accurate preliminary calculation, the selection of appropriate ventilation equipment, installation and commissioning works. One of the main stages is also the design of the ventilation system.
HIGH TEMPERAURE EXHAUST FANS
Fans with ambient air cooling systems handling hot airstreams must have sufficient airflow and be kept in operation until airstream temperatures cool below 120 F to prevent damage to the fan unit.
REINFORCEMENT OF BLOWER WHEEL
Blower Wheel is a rotating device consisting of number of fan blades mounted on a hub with drive shaft that forces the air/gas in the desired direction with increased pressure. To meet the demands of large scale applications in industries, centrifugal fans are custom designed as double inlet impeller and multistage impellers where two or more single inlet impellers are mounted back to back on the same shaft. Industries with large capacity plants which require high pressure airflow use these types of fans in their process applications.
