||DOSH Guidelines are benchmarked against which standard/guidelines?
||Referenced to CDC & EPA of USA, WHO, ASHRAE Guidance, and Singapore Guide. Note that further references are also listed under each of the DOSH Guidelines.
||ASHRAE has been formed in 1986. Prior to Covid 19 why was the importance/publicity/awareness of technologies for indoor air treatment and sanitation not emphasised? Was it due to all the earlier airborne transmission viruses being manageable? Design of ACMV system for shopping malls place no emphasis on air treatment, but merely all about achieving the required indoor temperature. By right, attention on air treatment should always apply for design of healthcare, institutional offices or food production facilities.
||ASHRAE Malaysia Chapter was formed in 1986. ASHRAE was formed in 1894 and is committed to serve humanity by advancing the arts and sciences of heating, ventilation, air conditioning, refrigeration and their allied fields..
FYI, Malaysia Chapter organised the first ASHRAE IAQ International Conference in 2010 in KL - the very first time this Conference was held outside of USA. The event was supported by the Ministry of Health, Malaysia. IAQ has always been an important part of ASHRAE's activities but the current COVID-19 pandemic has made IAQ even more critical. Ventilation rate in conjunction with proper air treatment have been and will always be of importance in the HVAC industry for a healthy indoor environment. The required ventilation rates for different categories of buildings/applications are emphasized in building codes and design standards. Meanwhile, ASHRAE standards are being continuously reviewed for improvement and relevancy.
||Are Personalised Ventilation (PV) and Personalised Exhaust (PE) systems applicable to Healthcare setting only?
||While the study on PV & PE was focused on healthcare setting but the findings are universal. They are to be seen as “task or personalised ventilation” and “local or personalised exhaust” strategy, and could be considered for other applications as well.
||What is the effectiveness level of the various options if one cannot implement proper ventilation as per the DOSH Guidelines?
||The basic requirements such as ventilation rates need to be met. One of ASHRAE's core recommendations is to conduct system re-commissioning to verify that the ACMV systems are functioning as designed, including the ventilation rates. The selection and effectiveness of other options will depend on the risk assessment and deficiencies identified in the exisitng system.
||Will normal exhalation (exhaled air) rise up into return grilles located at 2.7m FFL height?
||Exhaled air which potentially carries infectious aerosols, can remain suspended and follow the air stream. The air flow patterns (MV or DV) will eventually carry these infectious aerosol laden particles to the return grilles.
||Since airborne virus transmission risk is higher in an enclosed space, can we consider to adjust elevator (lift) car doors for buildings to be opened instead of being closed whenever the elevator is not in use (idle mode) as a good practice?
||Good comment. However, safety considerations mandate lift landing doors to be closed except under fire mode operation (and even then, it is limited to the ground floor landing doors).
||In an UFAD system, will the heavier aerosol droplets descend downwards against the flow of the rising air stream towards the return path?
||Particles larger than 10 microns tend to sink downwards and not be airborne. Although there are ongoing studies on the risk of re-suspension of heavy droplets, TDV (DV and UFAD) are normally designed with low air velocity whch would mitigate against airborne re-suspension. Regular disinfection of the floor and floor outlets will be necessary.
||Based on the 3 types of air distribution strategies. which one is the best? MV, DV or UFAD?
||There are basically 2 main air distribution strategies. Overhead - Mixed Ventilation (MV), and Low Level - Thermal Displacement Ventilation (TDV) which comprises UFAD (for comfort cooling to avoid cold feet phenomena) and DV. Both strategies have their merits and demerits depending on the design objective.
||Is there any actual PV installation already implemented or is this still at research stage?
||PV setup is available at NUS Field Environmental Chamber - this is a typical seminar/classroom size (about 65 m2) with external wall, window, false ceiling etc. There is an actual installation of PV integrated with UFAD at the BCA Zero Energy building.
||Would installing a centralized exhaust fan for an enclosed room be sufficient to ensure the contaminated air is diluted?
||A central exhaust fan would work but the number of exhaust grilles in an enclosed room would be a critical factor. Ideally, we need to remove contaminated air (even for a MV strategy) in a “localised” manner.
||Is there a continuing study for a current set up in Malaysia or Singapore where people are vaccinated and masked?.The studies presented appear to be for the pre-vax and without mask days.
||If the question posed relates to PV-PE, then there are no such studies yet. Although the earlier work was pre-COVID, the setting considered was infectious aerosol (using tracer gases). Hence, the findings are relevant and applicable in the COVID setting from an engineering control perspective.
||To assess the adequacy of ventilation, measurement of ventilation rate is required. What will be the proper measuring instrument to use and what are the parameters to be based on?
||Use a CO2 measurement instrument placed at the breathing zone height. CO2 ppm is a surrogate for ventilation (Outdoor Air) quantity. One could also directly measure the outside air quantity at the OA intake at the AHU.
||Is there any study from reputable organisations of dosage of Ozone concentration required to kill Covid?
||Vendor: There are a few international universities that have done such studies. Fujita Health University is one of the few.
||Is the function of sterilization technology similar to HEPA or MERV 13 filters? If it is, is the efficacy or efficiency of this technology better than HEPA filters?
||Vendor: HEPA filters do not perform sterilization, they capture the airborne particles. The sterilization technology focuses on deactivating the viruses or pathogens in the indoor environment where the source is.
||Should property developers design buildings with full cross ventilation in newer developments rather than the current designs with fully enclosed and non-openable windows?
||For residential setting, natural ventilation provision mandated in the building bylaws are adequate. As recommended in DOSH IAQ guidance note for residential setting, occupants of residential homes can improve their home ventilation by opening windows and doors, especially in the mornings and the evenings when outdoor air is cooler. If there is concern of mosquitoes and insects, mesh screens can be fitted.
||For Cerafusion application, is there any uncertainty on ozone measurement at 0.05ppm and what is the uniformity and reproducibility contribution using ozone swap test?
||Vendor: End users normally carry out their own swab tests on ozone levels before they implement Cerafusion. As an example, Changi Airport spent almost 2 years testing the technology before implementing in their facilities. Similarly, RWG spent a lot of time testing the technology prior to implementation.
||Regarding the low ozone Cerafusion technology, how does it comply to the IAQ acceptable limits of 0.05ppm as the unit will inevitably emit more than this concentration limit?
||Vendor: In an actual measured implementation, the ozone level is controlled to be within 0.05ppm, thus complying to IAQ standard.
||Is there any study from a reputable organisation on dosage of Ozone concentration required to kill Covid virus?
||Vendor: Yes, there are few international universities and many other research studies. Fujita Health University is the first to come out with a study based on use of low ozone concentration. The rest of the studies tend to use higher ozone concentration.
||Is UVC disinfection a means to kill or inactivate Covid virus? If so, what type of UVC devices are most suitable for an indoor Mall application?
||Vendor: UVC lamps installed in an AHU is a good consideration. Ensure proper sizing (15J/m2 dosage is recommended by ASHRAE COVID-19 Epidemic Task Force)
||With UVGI installed between the Cooling Coil and Blower, will the maintenance for belt, motor & greasing become difficult?
||Vendor: For older AHUs, where the space between the coil and motor/blower is limited, it could pose a challenge. Hence, care should be taken to prevent damage to the lamps and the use of encapsulated lamps is recommended.
||Are there any case examples of upper room UVGI application in a natural/mechanical ventilated high ceiling workplace (i.e. with no air conditioning)?
||Vendor: Related study can be found @ https://pubmed.ncbi.nlm.nih.gov/25928547/
||What type of certificate is issued by an authorized UV lamp supplier?
||For upper room UVGI system, what verification/testing can be conducted by the customer to ensure that it is working effectively against Covid-19?
||Vendor: The customer can ask for the measured UV dosage readings to ascertain it is sufficent for the desired upper room application and also not exceed the limit at eye level.
||Mould will propagate at what indoor conditions? 26C / 70%RH?
||As a general guide, mould will propagate should the indoor room RH constantly exceeds 70% in the equatorial climate region.
||DOSH IAQ Guide says to turn off heat wheel for non residential & public areas. For a new project with a dedicated outdoor air system and centralized exhaust, can the heat wheel continue to operate? .And what specific precaution to be taken?
||The recommendation to disable the heat wheel is to avert cross-contamination. If heat wheel is to continue running, then precautionary measures will have to be taken to mitigate the risk of cross-contamination such as provision of enhanced air treatment for the air stream after the wheel.
||Any advice on the reduction of airflow when replacing Air Filter from MERV 6 to MERV 13? Will the airflow reduction be significant and affect the cooling capacity?
||Vendor: You will need to check the capacity of your existing ACMV system to determine whether the external static pressure of the AHU blower can cater for the increased pressure drop of MERV 13 filters, or with the resultant reduced airflow, will the ACMV performance (cooling capacity, air movement, ACH etc) still be acceptable.
||Will the static pressure increase when replacing with MERV 14 filters to an existing system?
||Yes, the higher the filter grade, the higher is the pressure drop.
||Does plasmacluster ioniser help to minimize virus count in the air?
||At the moment, there is yet to be any conclusive evidence with regards to the effectiveness of ioniser on inactivation of SAR-CoV-2 (Covd-19) virus. Consumers are advised to consider use of such system/technology wisely.
||Is there a recommended standard for maintenance and disposal of air filters in conjunction with their increased use to mitigate transmission of Covid-19? Are there any known cases of outbreak due to improper handling of air filters?
||You may refer to ASHRAE website https://www.ashrae.org/technical-resources/filtration-disinfection under the heading :
HVAC System Maintenance and Filter Replacement during the COVID-19 Pandemic.
We do not have knowledge of any case of outbreak due to improper handling of the filters being reported. However, it is strongly advisable that precaution and proper procedures are strictly observed for filter media replacement.
||If replacement with MERV 13 filters introduces an additional pressure drop of say, 50-100 Pa, what will be the corresponding percentage drop of the air flow rate?
||Vendor: The change in flow rate due to increased pressure drop can be read from the fan performance curves. There is also the need to consider the final pressure drop of the selected filter when it is fully laden with filtered particles before replacement.
||How detrimental is UVC to the air filters? Will it shorten the filter lifespan or render it unusable? Any hazardous emissions expected? What is the selection criteria for pairing filters with UVC?
||Vendor: For air filter media which is unable to resist UV, the media will rupture. There is no hazardous emission. If UV sterilizer is to be installed in the system, do check the properties of the air filter media for UV resistance compatibility, and also adhere to the recommended distance between UV sterilizer and filter.
||Which is more effective - HEPA filter or UVGI for an AHU?
||Vendor: As long as they are installed properly and adhering to the Supplier's instructions, they are both effective. However, do take into consideration the impact of other parameters such as static pressure, operating power consumption, installation space, etc.
||Should HEPA filters inside the AHU be placed before or after the cooling coil (or after the supply fan) for better performance?
||Vendor: Typically the HEPA filter is best installed as 'late' as possible in the air system flow. However, for existing installations, there will be various constraints that will dictate the decision making at site.
||Most recommendations on enhanced filtration for ACMV system are applied at the intake side/section. Why not at the exhaust side so as to clean the air before discharging to the environment?
||Use of enhanced filtration to treat air before discharging to the external atmosphere is only considered if the indoor air to be discharged emanates from a hazardous or potentially highly contaminated source. Otherwise, the mother earth atmosphere is the perfect air space for dillution.
||Do DV and MV will have similar air flow rates? Cold air tends to drop/stay at bottom compared to hot air which tends to float. Please enlighten.
||Presumably the query refers to only airconditioning for the MV and DV strategies. For comfort cooling i.e. office setting, the typical MV system will be about 6 ACH to cater for the cooling load. Whereas for TDV (Thermal Displacement Ventilation) using UFAD, it will typically be up to 9 ACH due to the design of higher supply temperature . However, if TDV is used for transient space (where cold feet phenomena is not a problem for the shorter occupancy duration), the ACH can even be lower than MV with the advantage of stratification consideration.
||Besides AHU application, can MERV 13 filters be used for FCU ( i.e. Ducted type FCU, Cassette Units, Wall Mounted split units)?
||The available static pressure for fan coil units will likely be too low to overcome the additional pressure drop of MERV 13 filters. For free blow units such as Cassette and Split units, the fan static pressure is definitely insufficient.
||What is the uncertainty associated with 5ppb Ozone quoted?
||The 5ppb is referred to in UL2998 to qualify zero ozone emision product
||How may the ACMV Engineer ascertain the effectiveness of UVC in an AHU or ducting? What is the testing criteria or standard that governs the UVC compliance for the medical health application?
||Vendor: For coil maintenance, do a bacteria and mould swap test before UVC installation and at least 3 weeks after installation. There should be at least over 90% reduction post installation
||After the HEPA filters have 'captured' the Covid virus, what are the precautionary measures to be taken to dispose these filters?
||Vendor: For servicing of HEPA filters in hospital, the technician needs to wear full PPE and disposal of the filter needs to be carefully and properly carried out by bagging or wrapping them after removal for proper disposals in trash bins.
||Among all the enhancement methods availabe in the market, if I have limited budget, which method should I choose?
||Vendor: The most practical way is based on dilution technology. Open up windows to bring more outdoor air into the building to dilute the indoor pollutants . It will reduce the transmision of virus. Extra air cleaning technology ought to be a secondary option when you can't bring adequate outdoor air into the building.
||Suggest for need to carry out CFD at certain sensitive areas as there are many cases where the airflow direction is not really properly studied. Even in hospitals, there are cross contaminations due to this.
||Vendor: Besides CFD, you can conduct smoke test to check the air flow directon in the sensitive area.
||Apart from EPA test certificate for UVC, what other certification can we have in Malaysia or SEA region?
||Vendor: In Malaysia, you may consider SIRIM, TUV or equivalent.
||Is it true that increasing exchange rate (recirculation) will lead to increased risk of cross contamination? And increasing outdoor air will help to decrease the risk of cross contamination?
||Increasing airchange of recirculated air without increasing the outdoor air intake and/or using proper air treatment (e.g. MERV 13 filters) will likely increase the risk of airborne transmission. The proper approach is to increase air dilution by increasing outdoor air intake in conjunction with maintaining desired indoor temperature and relative humidity.
||UVGI affects plastic/composite materials directly exposed to it and this applies to air purifiers, FCU's, AHU’s and etc. Does ASHRAE have guidelines or case studies on this topic?
||You may refer to ASHRAE website https://www.ashrae.org/technical-resources/filtration-disinfection.