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Frequently Asked Questions and Glossary of Terms

FAQ / Glossary

This page is updated as new information becomes available.

General Recommendations | Review of current operational practices | Holistic view for owner/operator | Pandemic preparedness plan | Indoor and outdoor environment | Review the space typesOperate and maintain HVAC | Air conditioning and ventilation systems | Exhaust Systems | Pressure Control | Elevator Control | BAS and Access Control Systems

General Recommendations

Operating commercial office buildings under epidemic conditions requires a holistic framework during the crisis and the restoration to potentially a new “normal” after the public health emergency has ended. Considerations include:

  • Review of current operational practices
  • Holistic view for owner/operator

Review of current operational practices | Return to Top

  • Modes of operation of HVAC systems
    • sequences of operations
    • set points
    • schedules
  • Verification that equipment and systems are properly functioning and have the enhanced capabilities to address public health considerations, with a focus building air circulating systems.
  • Understanding that infected people who are asymptomatic may enter buildings, increasing the likelihood of the spread of virus through air systems to other occupants.

Holistic view for owner/operator | Return to Top

Owners and operators should take a holistic view of their buildings and:

  1. Develop a pandemic preparedness plan
  2. Review indoor and outdoor environment
  3. Review the space types
  4. Operate and maintain HVAC
    • Air-Conditioning and Ventilation systems
    • Exhaust systems
  1. Check Pressure Control
  2. Check Elevator Control
  3. Check BAS and Access Control Systems

Develop a Pandemic Preparedness Plan | Return to Top

Consider these possible goals:

  • Reduce the spread of infection among building occupants,
  • Maintain HVAC and Building Service Systems in safe and healthy conditions,
  • Minimize impact on building occupants and visitors,
  • Communicate risks and precautions being taken with occupants transparently
  • Implement measures that help make occupants feel secure:
    • Require occupants, visitors and maintenance personnel to wear appropriate PPE per CDC,
    • Screen, monitor and control the circulation of occupants and guests to help avoid transmission of disease,
    • Increase frequency for surface disinfection on frequently touched surfaces, such as door handles, handrails, door bells and elevator buttons.

Ensure continuity of supply chains and have backup plans.

  • Identify your critical suppliers, e.g. filters, cleaners, disinfectants, parts, PPE, etc.,
  • Identify vendors who could negatively affect your operation if they fail to deliver,
  • Review current service provider agreements to see if alternate suppliers can be engaged in the event of a supply disruption, for example, equipment service providers, and understand contract limitations and restrictions on using alternative providers,
  • Ask critical suppliers to share their pandemic plans:
    • What does their plan include?
    • Have they tested their plan? When was it updated?
    • Set boundaries with suppliers – ask that they do not send staff who may be showing signs of illness to your property.

Review contract agreements:

  • Review contract agreements: Review contracts with tenants, residents, service providers, utilities, and suppliers to determine what rights and remedies they have because of disruptions due to unforeseeable circumstances that prevent fulfillment of a contract.

Establish a communication protocol and continuity of operations plan:

  • Identify key contacts and publish normal and emergency contact information,
  • Document the chain of command and communication requirements, and provide instructions and outline expectations for how all responses are to be documented and what records shall be maintained and distributed.

Provide staff with:

  • PPE per CDC and OSHA requirements,
  • Training on the proper use and disposal of PPE and waste,
  • Training on infection prevention and control measures,
  • Cross training to ensure critical building functions are maintained in an emergency, and
  • Instruction to staff to stay at home if they are feeling sick.

Check with insurance providers to determine whether there are special measures that can be taken to preserve coverage or lower premiums.

Next Steps:

  1. Notify staff, tenants and visitors about the plan
  2. Follow all local, state and federal executive orders, statutes, regulations, guidelines, restrictions and limitations on use, occupancy and separation
  3. Follow OSHA Guidelines, especially the portion in the guide regarding filter and outside air.
  4. Ensure that custodial staff and service providers job descriptions includes performing proper cleaning procedures based EPA and CDC guidance using approved products and methods:
    • Disinfect high touch areas of HVAC and other Building Service systems such as on/off switches, and thermostats;
    • Disinfect interiors of refrigerated devices, such as refrigerators, coolers and vending machines where the virus can survive for potentially long periods of time.
  1. Consider installing a thermal camera at building entrances to help screen visitors   for elevated body temperatures. Note that that infected individuals may show no   signs of being ill, including having no fever, and can be responsible for much of   the transmission. In such cases, thermal imaging may not be effective.
  2. Where modifications to existing HVAC systems are not possible due to physical   or capacity limitations, install portable filtration and air cleaning devices such as   UVGI (Ultraviolet Germicidal Irradiation), especially if seniors or anyone with other   health issues or compromised immune systems may be located, or, in mission   critical areas where required.
  3. Provide automatic hand sanitizer dispensers in the high touch areas and other   common areas, including spaces where equipment where frequent maintenance   is required, and ensure dispensers are serviced often and remain operational.
  4. Post signage in prominent locations that contain information and instructions to   educate and remind staff about proper procedures to maintain personal   protection while cleaning, replacing filters and moving or using other equipment   that maybe contaminated
  5. Consider adding air treatment and cleaning devices such as. UVGI (ultraviolet   germicidal irradiation) in duct, plenums and air handling units and on the face of   cooling coils. Refer to filtration and disinfection guidance here.
  6. Consider providing antimicrobial door mats at high traffic entrances to the   building.
  7. Institute additional cleaning procedures to ensure proper disinfection of   bathrooms, kitchens and common areas. Educate cleaning and maintenance staff on proper personal protection and PPE use including following OSHA worker   exposure guidelines.

Review Indoor and Outdoor Environment | Return to Top

  • Maintain dry bulb temperatures within the comfort ranges indicated in ANSI/ASHRAE Standard 55-2017
  • Maintain relative humidity between 40% and 60%.
In Cold Climates In Warm Climates
i. HVAC systems with no humidification may not achieve the minimum humidity indicated,

ii. Observe building assemblies and finishes frequently for condensation when indoor dew points rise above the surface temperatures of the assemblies and finishes,

iii. Excessive humidity may lead to condensation, indoor mold growth, and degradation of indoor air quality.
i. HVAC systems without dehumidification or without Dedicated Outdoor Air Systems may not reduce humidity to the maximum percentage indicated

ii. Observe building assemblies and finishes frequently for condensation when cold surfaces in contact with or near air distribution devices (grills and registers) ducts and equipment casings are below indoor dew points,

iii. Excessive humidity may lead to condensation, indoor mold growth, and degradation of indoor air quality.

Review the space types | Return to Top

Atriums Atriums require tenants on different floors to carry out similar social distancing, personal protection practices, pressure differential, similar filtering efficiencies, similar air treatment, etc. for disease transmission reduction measures to be effective.
Conference Rooms Keep doors to be opened to promote good ventilation where possible. If doors must be closed, consider local air filtration and cleaning devices and appliances such as portable air filters, or provide local exhaust fans discharging directly to the outside to improve ventilation.
Pantries/Storage Rooms Provide local exhaust, or portable air filtration and cleaning appliances, especially if refrigerators, or similar appliances, are presented.
Public/Large Assembly Spaces Where there can be a large assembly of people, consider air treatment, e.g. upper-room UVGI lamps.

Operate and maintain the HVAC system | Return to Top

Building owners and service professionals should follow the requirements of ASHRAE Standard 180-2018, Standard Practice for the Inspection and Maintenance of Commercial HVAC Systems which has tables to show the typical maintenance required for equipment that has been in operation. Consider PPE when maintaining ventilation materials including filters, condensate. Consult additional guidance before duct cleaning. Check specifically:

  • Dampers, filter, and economizers seals and frames are intact and clean, are functional and are responding to control signals.
  • Zone and air temperature, humidity and CO2 system sensors, as applicable, are calibrated and accurately reporting environmental conditions to the BAS or local controllers.
  • Air Handling systems are providing adequate airflow, there are no blockages in the duct system (for example – closed fire/smoke dampers) and air from the air handling system is reaching each occupied space.
  • Exhaust fans are functional and venting to the outdoors.
  • Check outside air intake regularly for any potential risk such as exhaust nearby and provide proper clearance if assessible by pedestrians, etc.
  • Update or replace existing HVAC air filtration to a minimum of MERV 13 (MERV 14 preferred) or the highest compatible with the filter rack, and seal edges of the filter to limit bypass. Make sure the air handling systems and fans can overcome the additional pressure drop of the new filters and still maintain air flow at acceptable levels.
Operate and maintain the HVAC system – Air conditioning and ventilation systems | Return to Top
  • Continued operation of all systems is recommended.
  • Outside air for ventilation be increased to as much as the HVAC system can accommodate and still maintain acceptable indoor conditions during occupied hours.
  • Flushing sequence or mode may be implemented to operate the HVAC system with maximum outside airflows for two hours before and after occupied times.
  • Systems may be operated at minimum outside air settings when the building is unoccupied or not operating in the flushing mode.

Centralized and floor-by-floor Variable Air Volume (VAV) systems: General information

  • For central or floor-by-floor VAV systems that have the capacity to operate with 100% outside air, such as an economizer cycle, close return air dampers and open outdoor air dampers to 100% or to the maximum setting that the HVAC system can accommodate and still maintain acceptable indoor conditions.
  • If there are heating and cooling coils to temper the air, it can provide comfort and eliminate recirculation (in the mild weather seasons this will have smaller impacts to energy consumption, thermal comfort, or humidity control, however, using 100% outside can be more difficult in extreme weather conditions).
  • Considerations also should be given in areas with dry outside air that may lower the relative humidity to below 40%.
  • Prioritize increasing outside air over humidity (see concerns about operating at indoor humidity outside the range of 40%-60%.

Centralized and floor-by-floor Variable Air Volume (VAV) systems: Floor-by-floor

  • In floor-by-floor VAV systems that have only minimum outside air damper positions or openings, open outside air damper to its maximum position (the same cautions and concerns stated above apply).
  • If outside air is supplied centrally from outside air handling units (typically at mechanical levels) to all floors, and there are unoccupied tenant floors, divert the outside air to the occupied floors.
  • Consider changing the floor level VAV air handling units' discharge air temperature setpoint the maximum (typically no higher than 60º F).
  • This will cause VAV terminal units (boxes) to open to try and satisfy space cooling loads which will increase the number of air changes in the space being served.

Centralized and floor-by-floor Variable Air Volume (VAV) systems: Heat or energy recovery

  • When heat or energy recovery devices such as heat wheels or enthalpy wheels used in air handling systems and DOAS and the systems serves more than one space, care should be taken to determine whether the energy recovery device should remain in operation or be shut down.
  • Some energy wheels have the potential of cross contamination between the intake and exhaust air stream.
  • Refer to ASHRAE specific guidance on energy recovery device operation during epidemics and pandemics for further guidance.
  • Other heat recovery devices that decouple the intake and exhaust air steams such as run around coils, plate heat exchanges, and heat pipes can continue to operate.
  • Heat wheels may continue operation if the unit serves only one space.

Centralized and floor-by-floor Variable Air Volume (VAV) systems: Cooling coils

  • Cooling coils, heating coils, condensate drain pans, and humidifiers inside air handling equipment can become contaminated.
  • Therefore, consider adding UVGI for coil surface and drain pan disinfection are encouraged as it will reduce the needs and frequency for in-person coil surface disinfection.
  • These devices and systems should be monitored often and regular and emergency maintenances should continue.
  • Provide PPE protection for building operators, maintenance technicians and anyone else who must inspect or come in contact with the device or equipment.

Centralized and floor-by-floor Variable Air Volume (VAV) systems: Operable windows

  • In buildings with operable windows, when outside air thermal and humidity conditions and outdoor air quality are acceptable, open windows where appropriate during occupied hours.
  • Disabling the interlock between opening windows and air conditioning system lockout or shut down if this feature is provided for in the Building Automation System.
  • Monitor indoor spaces for possible contaminants entering through the windows such as toilets exhaust located nearby or for windows assessible to public and high traffic on adjacent streets and walkways.
  • Exposure to seasonal and other outdoor allergens (pollen and mold spores) may occur with windows opened.
  • Special ductwork cleaning, or, changing filters more often than normal is not necessary.

Heating Water systems:

  • Keep heating water systems circulating and maintain temperatures above 140°F to avoid microbial incursion. Do not let water temperature to drop below 120°F.
Operate and maintain the HVAC system - Exhaust systems | Return to Top
  • Exhaust system for toilets should run 24/7. Do not open operable windows in toilets.
  • Garage exhaust systems should run two hours before occupancy. It is preferred to run garage exhaust systems continuously during occupied hours. Continue to operate garage exhaust systems 2 hours after the building becomes unoccupied. These measures may require disengage the demand ventilation controlled by Carbon Monoxide.
  • Other exhaust systems should continue to run as normal. Run exhaust systems 2 hours before and after occupied periods.
  • If there are exhaust outlets located in pedestrian areas outside, provide warning signs and consider diverting or rearranging the exhaust air discharge locations so that they would pose no opportunity to cause harm.
  • Temporary and Special exhaust systems:
    • Consider installing temporary and special exhaust systems if there are rooms that may accommodate infected people or have the opportunity generate and entrain harmful particulates in the air. Particulates or aerosols should be captured and filtered or disinfected as close to the source as possible. Particulates can possibly be a means where the virus can adhere to become aerosol.

Pressure Control | Return to Top

  • Maintain equal pressures on all the floors in multi-floor buildings. Maintain slightly positive pressure as compared to outside in both single story and multistory buildings. Shut off return air to the central air conditioning systems in the spaces where infected people may be present and use exhaust fans discharging air directly to the outside away from outdoor public gathering spaces, outdoor air intakes and operable windows. Consider HEPA filter, or, UVGI lamps with exhaust fan if exhaust can cause harm to public.
  • In tall buildings, pressurizing the building will need to take into consideration of stack effect and wind effects. Stack effect direction can be reversed between summer and winter; therefore, settings likely will need to be adjusted throughout the year to maintain the above recommended conditions. To help mitigate stack effect, close all the doors in public areas along the path of least resistance where stack effect is strongest such as at elevator shafts connecting all floors, atriums, open stairs, escalators, etc. to isolate air transfer between floors. Consider providing signage to inform occupants to keep these spaces closed off.
  • Tenants and visitors should use revolving doors and properly designed vestibules in buildings that have these types of entrance and exit ways rather than using single swinging doors to enter the building. Caution should be taken when going through air-locks by allowing social distance to “air” the space after the passage of a person. Consider providing signage to inform and direct occupants as to what entrances and exits to use.
  • Wind speed and pressure in the upper part of a tall building can be significantly higher than lower levels. Pressure control, especially the upper part of a tall building, needs to consider the wind pressure. Buildings with operable window in mild weather can increase the air changes more in the higher levels.

Elevator Control | Return to Top

  1. Turn on elevator cab (lift) ventilation fans, where possible
  2. Encourage occupants to take stairs, where possible, especially when elevator lobbies are crowded.
  3. Allow elevators to run at high speed to minimize time in elevator.
  4. Close elevator lobby vestibule doors, if available.
  5. Consider local air treatment devices in frequently used lifts.

Building Automation System and Access Control System Programming | Return to Top

Building Automation Systems:

  • Automate the control sequences in this document as a "Epidemic Mode" operation that can be turned on, shut down or override, if needed, by manual selection of the operator.
  • Monitor the measures as described in this document and set alerts and notification to provide real time feedback to building operators and maintenance personnel where possible.
  • If the building system has sensors for PM 2.5 and PM 10 particulate monitoring setup alerts and notifications to notify tenants when high particulate counts occur.
  • Provide remote access to staff and trusted service providers who are responsible for operating and maintain Building Automation Systems, security, access control, information technology, fire alarm and life safety systems. Have written procedures and test remote access and secure access levels and permissions for all individuals prior to an emergency, if possible.
  • Monitor and trend indoor humidity if the system has the capability and setup alerts and notifications to building operators and maintenance personnel when conditions occur beyond the recommended range of 40%-60% RH.
    • Consider adding humidity sensors and monitoring if the system can accommodate adding this feature. Consider using local data loggers that monitor temperature and humidity if the BAS cannot. Place loggers in high occupancy spaces such as lobbies, atriums, conference rooms, and spaces deemed critical by facility managers to building function and safety etc.
  • For HVAC system that use Demand-controlled ventilation sequences we recommend disabling this feature for the duration of the crisis.
  • Regularly check battery backup and generator backup power supplies for BAS, Security, Fire Alarm, Life Safety, Lighting Control, and IT systems and IOT devices that must remain in operation.

Access Control Systems:

  • Post signage and communicate to tenants, and post visitors' procedures for entering and leaving the building that will minimize the time spent in public spaces.
  • Use touchless assess control system if available and where possible.
  • Require and enforce social distancing within public and shared spaces using signage.
  • Ensure that workspaces are situated to accommodate social distancing recommendations.

Information on these pages is provided as a service to the public. While every effort is made to provide accurate and reliable information, this is advisory, is provided for informational purposes only. These are not intended and should not be relied upon as official statements of ASHRAE.

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