Engineering Strategies for Airborne Diseases

ENGINEERING STRATEGIES for Ai rborne Di seases

INNOVATIVE IDEAS | INTEGRATED SOLUTIONS | SUSTAINABLE PARTNERS

©2020, AlfaTech Consulting Engineers All rights reserved

©2020, AlfaTech Consulting Engineers All rights reserved

E N G I N E E R I N G S T R A T E G I E S

E X E C U T I V E S U M M A R Y

SITUATION

SUGGESTED HVAC SYSTEM SOLUTIONS

SUGGESTEDELECTRICAL SYSTEMSOLUTIONS

The Transmission of airborne disease is a concern in commercial buildings. There are many uncertainties with the current Covid- 19 pandemic which is not confirmed to be airborne yet. However, the World Health Organization continues to recommend airborne precautions for circumstances and settings according to risk assessment.

Improvements can be made to HVAC equipment, controls programing and facility operations. The following options are discussed in more detail throughout this document.

Improvements can be made to electrical systems to minimize the spread of viruses, bacteria and other germs. The following options are discussed with more detail throughout this document.

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Increased Ventilation

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Air Disinfection (GUV)

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Air Filtration

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Surface Disinfectant

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Air Disinfection (UVGI)

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Touch Free Operation

• Temperature & Humidity Control • Air Direction & Space Pressurization Control • Restroom Exhaust Control • Sequence of Operations Updates • Facility Operations & Maintenance

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Emerging Technologies

OBJECTIVE

To reduce the risk of transmitting airborne diseases from infected individuals, through specific modifications to engineered systems in the building including operation changes and equipment upgrades. .

CONCLUSION These recommendations should be followed based on building risk assessment, and in conjunction with the Building Pandemic Management Plan. Impacts of these suggestions on the occupant comfort, building pressure control, energy usage and other systems should be considered and analyzed before implementation.

I

AIRBORNE DISEASES AND COVID-19

II

HVAC SYSTEM STRATEGIES

III

ELECTRICAL SYSTEM STRATEGIES

I

AIRBORNE DISEASES AND COVID -19

• Large droplets (around 100 m) released from an infected person will not move further than 2 meters (6.5 feet).

• “Droplet nuclei” is less than 5 m in diameter and small enough to be transported by air motion, including HVAC systems.

• It is known that the main routes of Covid-19 transmission are through droplets and physical contact.

• It has not been confirmed if the virus transmits through small airborne particles and aerosols. However there is a widely

publicized case study of a restaurant where the HVAC system is in question.* Additionally, studies on the aerodynamic analysis of the virus suggest that Sars-CoV-2 can be airborne and aerosol concentration is relatively higher in restrooms.**

* https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article ** https://www.nature.com/articles/s41586-020-2271-3

II

HVAC SYSTEM STRATEGIES

Increased Ventilation

01

Air Filtration

02

Air Disinfection & UVGI

03

Temperature and Humidity

04

Control of Air Direction

05

Restroom Exhaust Control

06

Sequence of Operation Updates

07

Facility Operations and Maintenance

08

H V A C S Y S T E M S T R A T E G I E S

O1

INCREASED VENTILATION – A MATHEMATICAL MODEL OF THE AIRFLOW ROLE ON AIRBORNE INFECTIONS

The Wells-Riley Equation

Nc: Number of new infections

S: Number of susceptible individuals

I: Number of infectors

Increased ventilation (Q) will reduce the number of new infections in the building

q: Number of infectious doses

p: Pulmonary ventilation rate per susceptible

t: Exposure time

Q: Flow rate of uncontaminated air

H V A C S Y S T E M S T R A T E G I E S

INCREASED VENTILATION

• Outside air has high bacterial diversity and low average pathogenicity. • Indoor air has low bacterial diversity and high average pathogenicity. • Increased building ventilation rates will help dilute droplet concentration. • Required ventilation rate is not clear, however maintaining low level of CO2 level could be a good indicator. • Forced Air Systems with airside economizers will have more flexibility to provide increased ventilation. However systems without air side economizers including fan coil units and radiant systems will be limited with this approach. • Buildings located near pollutant sources and freeways should take additional measures on ventilation air with higher efficiency filtration systems. • Higher ventilation rates will increase building cooling and heating loads. Existing system capacity should be analyzed to avoid comfort issues. Considering lower occupant density in buildings, it is anticipated that majority of the systems could handle higher rates.

H V A C S Y S T E M S T R A T E G I E S

O2

AIR FILTRATION – CENTRAL

Air Filtration systems are utilized to remove air borne contaminants from HVAC systems. Contaminants can be in form of particles and chemical gases and vapors. Conventional filtration systems capture particles by passing airflow through the media. The fraction of particles removed from the air is termed “filter efficiency” and is provided by the Minimum Efficiency Reporting Value (MERV) under standard conditions. These systems are not very effective in removing gas and vapor molecules. • MERV 13 or greater are efficient at capturing airborne viruses. • MERV 14 filters are preferred. • HEPA filter efficiencies are higher than MERV 16 but will have higher pressure drops . Carbon filters are effective with chemical gasses but cannot be utilized for capturing airborne viruses. Utilization of carbon filters on outside air can be beneficial in areas with poor outside air quality. Filtration systems utilize different mechanisms for capturing particles. “Straining” captures particles larger than the openings on the media, but it is not the only method. Inertial impingement, interception, diffusion and electronic effects allow capturing particles that are smaller than the filter openings.

Silt

Gravel

Sand

Volcanic & Industrial Ash

H V A C S Y S T E M S T R A T E G I E S

AIR FILTRATION – DYNAMIC FILTRATION

Dynamic filtration technology can provide MERV 15 performance without ionizing or Ozone generation. Polarized fibers/screens collect charged particles and VOC. Conventional filtration system mainly collects particles at the face, but the dynamic media collects them throughout. This will allow more particle absorption and longer filter life. • Dynamic filters have lower pressure drop compared to traditional filters with the same MERV rating. • Maintenance cycle can be extended to over three years. • Less media changes also means less material use, less disposal costs and a smaller environmental footprint for the building. • Can be installed in package units and ducted fan coil units.

H V A C S Y S T E M S T R A T E G I E S

AIR FILTRATION – LOCAL

Portable filtration systems can be placed at locations with higher contamination & high traffic areas.

Ceiling mounted systems can be installed in areas where portable systems are not desired.

Unit placement and position should be determined in accordance with the existing HVAC system. • HEPA filters and UV Air Purification Systems can be included. • Added humidification function can also be included in dry climates.

H V A C S Y S T E M S T R A T E G I E S

O3

AIR DISINFECTION – NEEDLEPOINT BIPOLAR IONIZATION

This technology generates charged atoms or molecules called “ions”. These ions cause small particles to be either positively or negatively charged and create a magnetic effect. Opposite charged particles attach to one another, gain mass and surface area. Larger particles can be filtered in the air handling unit. When ions combine on the surface of the pathogen, they remove hydrogen form the pathogen and inactivate the virus . • The older technology called “Corona discharge ionization system” generates Ozone as a byproduct. Needlepoint system can limit the supplied power and eliminate Ozone generation. • This system is flexible and can be installed within units, ducts, ductless units etc. • Based on airflow rate and coverage area they come in different shapes. • The devices available in the market are self cleaning and maintenance free.

H V A C S Y S T E M S T R A T E G I E S

AIR DISINFECTION – ULTRAVIOLET GERMICIDAL IRRADIATION (UVGI)

Ultraviolet germicidal irradiation (UVGI) uses short-wave ultraviolet (UVC – 100 to 280nm) energy to inactivate viral, bacterial, and fungal organisms so they are unable to replicate and potentially cause disease. In short, UVGI does not kill viruses, it just deactivates them. • UVGI system is a cost-effective and a flexible solution. • Can be placed within ducts, Air Handling Units (AHU), plenum spaces, or in rooms above occupied areas. • Low electrical consumption if installed centrally within a unit-- approximately 2-3 kw for a 100k sf office building. • Ideal conditions are 200-400 fpm air velocity & 80-95F ambient air- dry bulb temperature.

H V A C S Y S T E M S T R A T E G I E S

AIR DISINFECTION – UVGI ADVANTAGES

There are additional benefits with inside AHU installations, such as:

Coil before UVGI

Coil after UVGI

• Prevents fungus & mold build up on the coil(s) • Coil pressure drop reduction by 10-15% • Increased heat transfer efficiency due to cleaner coil surface • No safety concerns with occupant exposure. • Increased Irradiance capacity allows higher predictive measures.

H V A C S Y S T E M S T R A T E G I E S

AIR DISINFECTION – UVGI DISADVANTAGES

Ozone

• Ozone production occurs with wavelengths below 240nm. • Titanium Doped (Doped Quartz - Ozone Free) quartz tubes prevent ozone production while natural and synthetic quartz materials still allow transmission.

Human Exposure

• Occupational exposure guidelines for UVGI have been developed by CDC/NIOSH. Exceeding the permissible exposure time can cause short- and long-term damages. • In-unit applications prevent human exposure and allow much higher irradiance.

Courtesy of Helios Quartz

H V A C S Y S T E M S T R A T E G I E S

AIR DISINFECTION – UVGI DISADVANTAGES

Material Degradation

Some materials degrade under UVC. Sealants, filter material and filter supports can be impacted on HVAC system. • Organic filter fibers and Hepa filters have an average of 5-6% weight loss versus fiberglass filter weight loss of 25% • Other than structural damage, polyester filters may crumble to the touch and lofted fiberglass may irritate eyes (fibers becoming airborne within ductwork) under UVC exposure. • UVC resistance ratings shown on Table 8 per ASHRAE RP-1509:

A – No effect (aluminum tape, all organic materials experience mass loss)

B – Minor Effect (mainly cosmetic changes)

C – Moderate Effect (some cracking/pitting)

D – Severe Effect (structural damage, not recommended)

Courtesy of Table 8, ASHRAE RP-1509

H V A C S Y S T E M S T R A T E G I E S

AIR DISINFECTION – PHOTOCATALYTIC OXIDATION (PCO)

UV light is applied to a metal oxide semiconductor material surface (typically titanium dioxide), super oxide and hydroxyl radicals are generated in the airstream. These highly reactive radicals and ions decompose organic compounds (VOC’s and pathogens) and turn them into CO2 and H2O. In short PCO deactivates bacteria and turns odors into air and water. • Possible by-products formed by incomplete oxidizing like formaldehyde, acetaldehyde, formic acid and acetic acid. Manufacturer data and published test results to be considered carefully. • Has been utilized in different applications with a proven track record. • Has a very low pressure drop (0.05” @ 500 fpm) • AHU retrofit options available with minimal space impacts.

H V A C S Y S T E M S T R A T E G I E S

O4

TEMPERATURE AND HUMIDITY

• Small droplets will evaporate fast under any relative humidity (RH), but higher space humidity levels slow the evaporation of large droplets. • Controlled humidity reduces transmission of certain airborne infectious organisms including influenza. • Breathing dry air can cause desiccation of nasal mucosa, which can make occupants more susceptible to respiratory virus infections. • Maintain dry-bulb temperatures per ANSI/ASHRAE Standard 55- 2017. • Maintain RH level between 40% and 60%. This could require humidification during dry & cold and dry & hot days. • Per REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations) Covid-19 guidance document, SARS- CoV-2 has been found highly stable for

2018 Study Humidity decreased Influenza A illness in pre-school

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14 days at 4C (40F)

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1 day at 37C (99F)

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30 minutes at 56C (133F)

H V A C S Y S T E M S T R A T E G I E S

O5

CONTROL OF AIR DIRECTION - OVERHEAD DISTRIBUTION

The majority of buildings in the USA are served by forced air systems. These systems can have either overhead or underfloor distribution systems. With overhead distribution, the conditioned air enters the space from supply ducts/diffusers installed over the occupied zone. The return air exits via return air plenums or diffusers positioned in the ceiling or full height walls. Overhead air distribution is designed to mix the entire air volume in an enclosed space and the air will circulate for longer and then reach occupants.

Any suspended pollutants or particles will linger for greater periods of time, resulting in lower air quality.

H V A C S Y S T E M S T R A T E G I E S

CONTROL OF AIR DIRECTION - OVERHEAD DISTRIBUTION

• This system is not very efficient with providing occupant isolation. • Workstation placement should be reconfigured to allow for supply and return air zones. This may result in further reduced occupancy. • HVAC system ductwork and diffusers should be placed accordingly so that workstations are not located within airstream. • Supplementary exhaust/transfer systems (ducted or unducted) can be considered to guide the air away from occupants at all times. • Portable filtration systems can be utilized in high traffic areas. • Personalized ventilation systems can be considered where other measures are not feasible. This option will require drastic infrastructure upgrades.

H V A C S Y S T E M S T R A T E G I E S

CONTROL OF AIR DIRECTION - UNDERFLOOR DISTRIBUTION

Displacement ventilation or underfloor installations are more efficient for pollutant control.

Fresh air enters the space from floor level and takes advantage of natural thermal buoyancy which sees warmer air rise towards the ceiling. Along the way, the air currents will force pollutants up and away from occupants, resulting in a much higher air quality.

In spaces with T-bar ceilings additional return grilles will reduce return air movement within the occupied space.

With this system the workstations can be reconfigured to create a layout similar to “hot aisle-cold aisle” configuration. Common supply air will be provided to the rows back to back and the return air will rise up from the middle rows. Diffusers placed in return rows will be shut closed.

H V A C S Y S T E M S T R A T E G I E S

O6

RESTROOM EXHAUST CONTROL

• Increase restroom exhaust rates as much as exhaust and make-up system capacities allow. • Maintain continuous exhaust (24/7). • Provide fresh outside air to restrooms in lieu of passive ventilation. Utilize reheat coils to prevent overcooling. (Ensure restrooms are still maintained under negative pressure) • Investigate make up / transfer air sources. install dedicated systems if necessary. • In addition to modifying restroom exhaust control, lowering toilet seat lids before flushing should be encouraged.

H V A C S Y S T E M S T R A T E G I E S

O7

RECOMMENDED SEQUENCE OF OPERATIONS UPDATES

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Increase the duration of building purge mode / flush mode to increase dilution. Start ventilation mode before occupancy.

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Run fresh air systems during nights and weekends.

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Run restroom exhaust continuously 24/7. Increase restroom exhaust rates if exhaust and make up system capacity allows.

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Monitor and control building humidity. Revise dehumidification and humidification modes and sequences as necessary.

❑ Maintain equal space pressures on all floors in multi-story buildings to avoid cross contamination between different floors. ❑ Maximize supply air reset sequence for buildings equipped with this sequence. This would allow more outdoor air and more air changes within the building.

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Disable demand-controlled ventilation and unoccupancy / vacancy sequences during scheduled business hours where possible. Use CO2 sensors for particle measurement only.

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Bypass Heat Recovery Systems with enthalpy wheels, where cross contamination cannot be avoided.

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Avoid cycling fan coil units on/off. Switch to constant volume operation if needed.

H V A C S Y S T E M S T R A T E G I E S

O8

FACILITY OPERATIONS AND MAINTENANCE RECOMMENDATIONS

❑ HVAC unit components (filters, coils etc.) can be contaminated. Take necessary precautions while servicing equipment.

❑

While working on roof, keep distance from sewer vent pipes where possible.

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Replace filters more frequently.

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Run restroom exhaust continuously 24/7. Increase restroom exhaust rates if exhaust and make up system capacity allows.

❑ Ensure CO2 sensors are working properly for monitoring (all zone and system level). ❑ If UVGI systems are applied, control human exposure. In duct / AHU systems should be provided with dedicated disconnects to service.

❑ Ensure UVGI compatible sealants and filtration system is utilized.

III

ELECTRICAL SYSTEM STRATEGIES

Air Disinfection

09

Touch Free Operation

10

Flexible Workstations & IES Recommendations

11

Overall Electrical Recommendations

12

E L E C T R I C A L S Y S T E M S T R A T E G I E S

09

AIR DISINFECTION – GERMICIDAL ULTRAVIOLET (GUV)

Germicidal Ultraviolet (GUV) uses short-wave ultraviolet energy (UV-C) in the 200 to 280 nm wavelengths to inactivate viruses, and to kill bacteria and fungal organisms so they are unable to replicate and potentially cause disease. Technically , GUV does not kill viruses it just deactivates them. • GUV is most effective in wavelengths of 265-270 nm and effectiveness drops off the further the UV is from this value. The optimum value varies depending on the type of germ. • GUV system is a cost effective and a flexible solution. • Can be placed or in rooms above occupied areas, within ducts and in Air Handling Units (AHU). Can also be used by robots in non- occupied spaces. • Low electrical consumption. Not included in lighting energy budgets.

E L E C T R I C A L S Y S T E M S T R A T E G I E S

AIR DISINFECTION – GUV OPTIONS

Upper Room Air Disinfection

• Inactivates virus directly in the room – safest option for occupants. • Permanent fixtures mounted above 7 feet continuously disinfect air in the space. • Best if used with low velocity ceiling fan to circulate air through the disinfection zone. • Saves energy. Only a couple of watts per room is needed. • Occupants should avoid direct exposure. Maintenance staff must be trained in safely operating the system.

Unoccupied Air Disinfection

• Robots using high powered pulsing xenon lamps can disinfect air after hours. • Not recommended for primary surface disinfection – hard to get direct access to all surfaces. Chemical disinfection has many advantages. • Doesn’t help during occupied hours.

E L E C T R I C A L S Y S T E M S T R A T E G I E S

AIR DISINFECTION – UVGI DISADVANTAGES

Human Exposure

• Occupational exposure guidelines for GUV in UV-C range have been developed by CDC/NIOSH. In room applications are usually limited to 0.2 W/cm2 for direct exposure. Exceeding the permissible exposure time can cause short- damage to eyes (irritation). No long- term damage has been documented.* • In-unit applications prevent human exposure and allow much higher irradiance.

Permissible exposure times for given effective irradiances at 254 nm wavelength

Material Degradation

• Paint can discolor under prolonged exposure. • Plastics can yellow under prolonged exposure.

* note: sunburn is caused by UV-B exposure. UV-C does not cause sunburn or skin cancer as it doesn’t penetrate the outer skin layer.

E L E C T R I C A L S Y S T E M S T R A T E G I E S

10

TOUCH FREE OPERATION

One strategy to minimize transfer of Viruses is to eliminate the need to touch common objects. There are many strategies to accomplish this objective include the following: • Sensor or biometrically activated, powered doors. • Smartphone or voice activated devices such as breakroom equipment. • Some controls systems like Comfy will control conference room features such as HVAC, lighting, plugs and could also be used for workstations. • Similar options available from Enlighted Bluetooth controls that can double as touch free door openers, etc. • Hands free, powered lavatories/soap dispensers/toilets/urinals in restrooms. • Voice activated elevator controls • Motorized blinds on automatic sensors.

Courtesy of Comfy

Courtesy of Lutron

E L E C T R I C A L S Y S T E M S T R A T E G I E S

11

FLEXIBLE WORKSTATIONS

Social distancing requires us to maintain a 6-foot distance from fellow workers. Many existing electrical and technology infrastructures in open offices are not designed to be flexible enough to allow re-configuration of workstations. Below are some strategies to be able to re-locate workstations as conditions change: • Provide a 6-inch raised floor. Provide a regular grid of boxes below the floor with 6-foot flexible connections (whips) to partitions. This will allow the electrical and data cables to be easily relocated as conditions change. • Provide a regular layout of flush floor boxes with power and data connections throughout the open office space. While not as convenient as a raised floor, this is a lower cost solution. • Provide power and data from the ceiling with drop cords in various fashions. Power poles, flexible drops and conduit drops can be used. Leave 6 feet of slack at the top to allow for relocation. While this option has poor aesthetics in fully fitted out offices with layin or hard lid ceilings, it works reasonably well in spaces with no ceilings or spaces with an ‘industrial’ feel. • Go to all wireless data to eliminate data cabling.

H V A C S Y S T E M S T R A T E G I E S

12

ELECTRICAL RECOMMENDATIONS

❑ Install permanent GUV fixtures above 7 feet aimed indirectly for continuous air disinfection.

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Install permanent GUV fixtures on ceiling aimed down for use only when space in unoccupied for air disinfection.

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Use a GUV robot to disinfect air and surfaces when space is unoccupied.

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Install sensor activated door openers.

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Install sensor activated plumbing fixtures in restrooms.

❑ Upgrade building automation controls to allow Bluetooth wireless devices to open doors, change lighting and temperature settings.

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Provide voice activated elevator controls.

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Provide motorized blinds.

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Provide flexible power in open offices.

INNOVATIVE IDEAS | INTEGRATED SOLUTIONS | SUSTAINABLE PARTNERS

AFRICA Beau Bassin, Mauritis Cairo, Egypt

EUROPE Vienna, Austria Le, Denmark Paris, France Berlin, Germany

ASIA Brahmanbaria, Bangladesh Dhaka, Bangladesh Dehradun, India Delhi, India Gandhingar, India Mumbai, India New Dehli, India

US San Jose, California

MIDDLE EAST Baghdad, Iraq Amman, Jordan

Wiesbaden, Germany Cologne, Germany Athens, Greece Madrid,Spain Zurich, Switzerland Istanbul, Turkey Birmingham, UK Bishop’s Strotford, UK Croydon, UK Edinburgh, UK Exeter, UK

LOS ANGELES Leamington Spa, UK Leeds, UK London, UK Luton, UK

San Francisco, California Los Angeles, California Atlanta, Georgia Edison, New Jersey

SAN JOSE Jeddah, Kingdom of Saudi Arabia Riyadh, Kingdom of Saudi Arabia Doha, Qatar Abu Dhabi, UAE

SAN FRANCISCO

415.403.3000 Bochum, Germany Frankfurt, Germany Hamburg, Germany Munich, Germany Ribnitz-Damgarten, Germany

213.212.9860 Maidenhead, UK Manchester, UK Nottingham, UK Stockport, UK Sunderland, UK Wakefield, UK

510 West 6 th Street, Suite 1105 Los Angeles, CA 90014

One Post Street, Suite 2200 San Francisco, CA 94104

1321 Ridder Park Drive, Suite 50 San Jose, CA 95131

Al Ain, UAE Dubai, UAE Madiant Zayad, UAE

Pune, India Rajkot, India

408.487.1200

Rostock, Germany Stralsund, Germany

Visakhapatnam,India Manilla, Philippines Singapore, Singapore Bangkok, Thailand