Feature
Continued from page 15
and scientific fields until recently , but as air quality needs change , they have been incorporated into many other application areas .
“ Engineers in the industry currently specify that HEPA filters must come with a test certificate , so each HEPA filter is issued with a specific certificate indicating the standard and test data parameters – this is commonly known as an MPPS Test Certificate and is widely considered essential . The certificate states a serial number and indicates the products rating achieved in the testing process – proving the manufacturing was completed correctly . Batch certification is not generally accepted in South Africa ,” says van Wyk .
Imported HEPA filters for the South African market primarily come from suppliers in Malaysia , Israel , Turkey , Germany and America and are in fact a very sensitive product . Only a very small surface area on HEPA filter is allowed to be repaired before being classed as un-useable .
HEPA filters are made from glass fibre material that has been pleated – it is supplied in rolls and then it goes into a pleating machine . As it is pleated , glue lines are laid down to hold the material together . Most of the companies around the world manufacture these filters in a clean room where the whole facility is contaminant-free .
Light Source
UV-C light example .
UV-C AS PART OF THE AIR FILTRATION PROCESS UV light is another common term in today ’ s industry lingo and is a relatively new technology in the HVAC sector for commercial applications . UV or ultraviolet light is produced in three main categories , UV-A , UV-B and UV-C .
The three types of UV radiation are classified according to their wavelength . They differ in their biological activity and the extent to which they react with living organisms . The shorter the wavelength , the more harmful the UV radiation .
Short-wavelength UV-C is the most damaging type of UV radiation . However , in its natural state it is completely filtered by the atmosphere and does not reach the earth ' s surface . UV-C can however be produced on earth and its effect is essentially damage to DNA and RNA , not allowing for cell replication , thus rendering a microorganism or virus inactive , or , in simple terms , killing it .
To-date no documented effects have been made in UV-C ’ s reaction to any steel or wood components , however the effect on plastics has been questioned considering the normal damage products experience outdoors .
“ UV-C lights are considered a combination solution with HEPA filters especially when it comes to viruses and bacteria as the filters catch , and the UV lights kill . So , as a combination they work effectively , and also offer safer handling in maintenance . One very important thing to remember is that when you are considering UV-C in system , the air needs to spend a certain amount of time exposed to the UV-C in order for it to be effective .
AC Expert
UV-C lighting typically found in an air purifier .
This is where a lot of confusion can come in when installing UV-C solutions because alone it cannot solve the problem of pathogens . For recirculating , this solution may be viable in future , but effectiveness comes down to airflow or several sections of ducting being fitted with UV-C lighting ,” notes van Wyk .
Verster adds , “ UV lights are also an expensive product , and effectiveness is directly linked to airflow vs the time of exposure , but there is honestly not enough research to indicate the time / exposure factor and how well this actually works at this stage . This is the same for the coronavirus generally – there are a lot of assumptions and now new research also indicates that dust particles can attach themselves to the virus taking it out of aerosol form . The available information is so vast and different . The only consistent recommendation from various world bodies is to increase ventilation . Although UV-C will kill all pathogens , scholars are also highly concerned with what other effects it can have on humans .”
THE MAINTENANCE DEBACLE WITH FILTRATION AND HVAC “ Maintenance is another big issue in our industry as most people know . Poor maintenance becomes a critical problem
www . hvacronline . co . za RACA Journal I November 2020 17