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FAQ PDF

  • Q1:What can I do in my home to reduce the risk of COVID-19 spread?

    A: ASHRAE recommends following guidance from the CDC which includes minimizing contact, having a household plan which includes basic information on how to protect yourself and how to keep your home sanitary.

    Additionally, follow the guidance in the Task Force’s Technical Guidance for Residences presentation which is intended to supplement CDC recommendations with options related to controlling virus transmission through the air using the home’s heating, ventilating and air-conditioning (HVAC) equipment and related factors.

    This Technical Guidance for Residences includes guidance for all homes, homes with forced-air systems, multi-family homes and guidance for homes with COVID-19 positive or high-risk individuals.

  • Q2: Should I operate my heating/cooling system in my home?

    A: Yes, guidance on how to run your residential Heating Ventilating and Air-conditioning (HVAC) system can be found in the Task Force’s Technical Guidance for Residences. This document includes guidance for all homes, homes with forced-air systems, multi-family homes and guidance for homes with COVID-19 positive or high-risk individuals.

  • Q3: Can my home heating/cooling system spread COVID-19?

    A: In general, a well-designed, maintained and operated heating, ventilating and air-conditioning (HVAC) system that meets applicable standards for ventilation and filtration will reduce the risk of transmission in your home. If, however, there is an infected individual, care should be taken to isolate them from the rest of the household which may include isolating parts of the HVAC system. See guidance for creating an isolation space.

    Note also that it is ASHRAE’s position that:
    Ventilation and filtration provided by heating, ventilating and air-conditioning systems can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air. Unconditioned spaces can cause thermal stress to people that may be directly life threatening and that may also lower resistance to infection. In general, disabling of heating, ventilating and air-conditioning systems is not a recommended measure to reduce the transmission of the virus.

    Guidance on how to run your residential heating, ventilating and air conditioning system can be found in the Task Force’s Technical Guidance for Residences

  • Q4: What can I do if someone in my home has COVID-19?

    A: When a household member is known to be infected, additional precautions are required in order to reduce the risk to other household members. The CDC has provided general guidance for this situation. A key aspect is to use a separate room essentially as an isolation space. The following additional actions should be considered when creating such an isolation space:

    • Select isolation space
    • Separate HVAC systems
    • Install air barriers
    • Operate exhaust ventilation

    Please see the Technical Guidance for Residences for more details.

  • Q5: What can I do if someone in my home is a high-risk individual?

    A: The CDC recognizes various categories of high-risk individuals and has general guidance for high-risk individuals. If there is not a known infected individual but there is a high-risk household member, additional protection can be afforded by creating a protected space for the high-risk individual. The following actions should be considered:

    • Select protected space
    • Separate HVAC systems
    • Install air barriers
    • Operate supply ventilation
    • Operate stand-alone air cleaner

    Please see the Technical Guidance for Residences for more details.

  • Q6: I want to upgrade the filter in my central heating and cooling system to a higher effectiveness one. Is this safe and do I need to adjust my fan setting?

    A: Generally, this is safe and some minor adjustments are in order.

    The typical 1-inch (thick) filter in most systems can be replaced with a filter up to MERV 13. Above this MERV rating the additional airflow resistance of high-performance filters may impact the performance of the HVAC system. If you have a 2-inch or greater filter then you can upgrade it safely with filters up to MERV 16. A 4-inch or greater filter will need to be changed far less frequently.  If installing a new filter grille or holder, consider one that can take a 4-inch filter.

    You will need to adjust the fan setting to make the fan run even if there is no heating or cooling. Many thermostats have a “fan only” setting that can be used or you may have a smart thermostat or fan controller that can be used to provide a minimum operating time of at least 15 minutes per hour.  In hot humid climates, be aware that continuous fan operation may reduce the ability of your system to control humidity. Please refer to the user’s manual of your system or consult an HVAC contractor for more information, and consider asking your contractor to upgrade your filters. Care must be taken when replacing filters because of exposure from surface contaminants.

  • Q7: I am considering using a germicidal ultraviolet system in my home, but I want to know if these systems produce ozone. Is there equipment I can buy that does not produce ozone?

    A: Yes, but it is important to avoid ozone production because it is a contaminant of concern. Look for equipment meeting UL Standard 2998 Environmental Claim Validation Procedure (ECVP) for Zero Ozone Emissions from Air Cleaners.

    This kind of germicidal equipment uses mercury vapor lamps that produce ultraviolet light at 254nm, which is effective at inactivating many pathogens including SARS-CoV-2. Light at this wavelength does not produce ozone, but the mercury vapor lamps also produce ultraviolet light at shorter wavelengths that do produce ozone. Manufacturers have overcome this problem by using titanium-doped quartz in the lamps, which block the ozone-producing wavelengths. These products require careful design, installation and maintenance to be most effective.

  • Q8: Will letting daylight into my home reduce COVID-19 risks?

    A: Perhaps. Direct sunlight has disinfectant properties in addition to having other benefits for people. Research has not yet determined exactly how strong that effect is for the SARS-CoV-2 virus. Window glass absorbs a lot of the ultraviolet frequencies where the disinfectant benefit comes from so, it is best to let sunlight in through open windows. However, this practice should only be used in addition to and not as a substitute for following all the recommendations from the CDC and the ventilation and air cleaning guidance found here. One must also take care to balance open windows with other concerns including thermal stress and pressure balancing.

  • Q9: Is it safe to continue use my ERV or HRV to provide ventilation in my single-family home?

    A: Generally, yes. While there can be a potential to recirculate a small amount of contaminated air if someone is infected, the ERV/HRV will still be an overall benefit in single-family homes.

  • Q10: Should I upgrade the outdoor air filter of my ventilation system to prevent the virus from entering my house?

    A: In general, it is not necessary to upgrade the filter treating the supply of outdoor air. According to current knowledge, there is a very low probability that the virus will enter from outdoors into the house through the mechanical ventilation system. In addition, a higher effectiveness filter may be more prone to clogging and will reduce air flow. One factor that might change this recommendation is if the outdoor air intake is near another building’s exhaust vent or near a location where people congregate.

  • Q11: My spouse and I are teleworking from home full time. Are the ventilation rates in ASHRAE Standard 62.2 enough for our dwelling?

    A: Generally, yes. If your work involves typical use of a computer and normal accessories and other routine office work, the ventilation requirements in ASHRAE Standard 62.2 should be enough. However, if your office work is more intense (e.g., heavy duty use of laser printers, use of a 3d printer, soldering or other activities not typically performed at home), you may wish to look to ASHRAE Standard 62.1 for guidance on adequate ventilation.

  • Q12: I run a stand-alone dehumidifier to minimize mold problems. Do I have to take precautions when emptying the condensate reservoir?

    A: Yes. Care should always be taken when disposing of condensate water as it can contain virus and other harmful contaminants. If possible, the condensate should be emptied outdoors or into a toilet. To avoid aerosolizing any potential virus, care should be taken not to splash when emptying the container and wearing a face mask is recommended. The container should be washed as should your hands after the operation is complete. If extra care is needed, such as if the dehumidifier is in an isolation space, consider using full PPE.

  • Q13: Is it OK to fix or replace my HVAC system, or do I need to wait until the pandemic is over?

    A: You should go ahead and fix or replace your system. As noted in Task Force’s Technical Guidance for Residences, it is important to maintain normal thermal comfort conditions. When replacing your system, consider including upgrades such as providing better filtration as discussed in the Residential Guidance.

    Some precautions you can take are to ask the contractor to use facemasks when they are working in your home.  You might also ask the contractor to only enter as few rooms in your home as possible, that you can clean after the work is done (or the contractor themselves may do this). Other additional precautions to consider if you are in a higher risk group are possibly to leave the home or use portable filtration in occupied rooms during the day while the work is being done.  You should definitely discuss these options with your contractor to make a plan that you are both comfortable with. Contractors may also have their own plans to protect you and their workers that should be part of any conversation before work starts in your home. For example, this protocol was developed by the Arkansas HVACR Association

  • Q14: Do I have to worry about infection from people standing around my outdoor air conditioning unit?

    A: Generally, not. The outdoor part of your AC unit is typically only connected to the indoors through refrigerant lines—not air ducts—and there is no transmission path for air.

    However, there are a few types of systems that do have outdoor air connections. Some window and portable air conditioners may pull in air from outside. In some large multifamily units, heating and cooling may be supplied by Packaged Terminal Air Conditioning (PTAC) units with similar outdoor air intakes. There may also be specific ventilation intakes unrelated to any heating or cooling system. In all these cases, social distancing rules are recommended between those intakes and people outdoors.

  • Q15: My home has wall-mounted ductless mini-split AC units. I know their filtration is minimal. Can I improve filtration of small and potentially infectious airborne particles?

    A: High efficiency particle filtration is rarely an option in such equipment. Instead, consider operating a portable air cleaner that has a high clean air delivery rate (CADR) in North America, a high clean air efficiency (CAE) in Europe (see additional info here), or is equipped with a HEPA filter and does not emit ozone. For more information, the EPA’s guidance to air cleaners and air filters in the home is here.

  • Q16: My condo apartment (or dormitory room) has horizontal, hotel-style AC units installed through the exterior wall. Can I improve filtration of potentially infectious airborne particles?

    A: High efficiency particle filtration is rarely an option in such equipment. Instead, consider operating a portable air cleaner that has a high clean air delivery rate (CADR) in North America, a high clean air efficiency (CAE) in Europe (see additional info here), or is equipped with a HEPA filter and does not emit ozone. For more information, the EPA’s guidance to air cleaners and air filters in the home is here.

  • Q17: My condo apartment (or dormitory room) has a vertical, hotel-style AC system installed in a side wall near the exterior wall. Can I improve filtration of potentially infectious airborne particles?

    A: High efficiency particle filtration is rarely an option in such equipment. Instead, consider operating a portable air cleaner that has a high clean air delivery rate (CADR) in North America, a high clean air efficiency (CAE) in Europe (see additional info here), or is equipped with a HEPA filter and does not emit ozone. For more information, the EPA’s guidance to air cleaners and air filters in the home is here.

  • Q18: I am reading that ozone can kill viruses. Should I get an ozone generator or similar product for my home?

    A: No. Ozone at high enough concentrations can inactivate the SARS-CoV-2 virus, but these levels of ozone are generally well above levels considered safe for occupant exposure. 

    For air cleaning devices, ASHRAE holds the position that

    Devices that use the reactivity of ozone for the purpose of cleaning the air should not be used in occupied spaces because of negative health effects that arise from exposure to ozone and its reaction products. Extreme caution is warranted when using devices that emit a significant amount of ozone as by-product of their operation, rather than as a method of air cleaning. These devices pose a potential risk to health

    Electronic air cleaning products have been known to emit ozone incidentally.  ASHRAE recommends products that have been certified as certified air cleaning devices by the California Air Resources Board  or as zero ozone emitting devices using UL 2998.

    For more information: the full text of ASHRAE’s position on filtration and air cleaning is here and the EPA guidance on residential air cleaners is here.

  • Q19: Is it OK to have a blower door test done on my house and if so, should I take special precautions.

    A: It is generally OK to have a blower door test if you do not currently have an infected or vulnerable person in your home. If this is the case, you should delay testing.

    A blower door moves a large amount of air, which in general should reduce the concentration of any virus-containing particles, but it can also re-suspend dust which might contain viral particles. For this reason, it would be best to stay out of the home and away from the blower door during the tests and at least an hour from the time the blower door is shut off, or if that is not possible to wear N95 masks. You should discuss safety with the contractor in advance to ensure they will be following company or manufacturer safety protocols that consider factors such as technician health, appropriate PPE, social distancing and surface disinfection. If both pressurization and depressurization tests are being done, it is recommended to do the pressurization test first.

    Blower door tests of occupied multifamily dwellings are not recommended at this time.

  • Q20: Will operating my evaporative cooler reduce risks?

    A: Yes, provided your unit ventilates the house with outdoor air. Direct evaporative cooling takes air from outside and cools it with evaporation and sends it indoors. This type of evaporative cooler will increase ventilation rate like an economizer or summer whole-house cooling fan and would similarly reduce risk. Some evaporative coolers do not take their air from outside and do not increase ventilation. Be sure to find out which type you have.

    Portable evaporative coolers may be helpful for comfort, they probably won’t reduce risks of airborne infection unless, like direct evaporative coolers, they supply outdoor air to the house.

  • Q21: I live in a tropical climate. I have no mechanical ventilation system because most of the day my windows are open, but for a few hours of the day I close my windows and turn on the air conditioning. What can I do to reduce my risk of COVID-19 infection during these periods?

    A: When there are periods of very low ventilation, a portable air cleaner can reduce the risk of COVID-19 infection. The best options include HEPA filtration and some sort of disinfection such as from UV-C. When buying electronic air cleaners, it is important to have them certified to be low ozone emitting. The Environmental Protection Agency has more information available on air cleaners for the home.

  • Glossary

    CIDRAP = U of MN Center for Infectious Disease Research and Policy

    DMHC = ASHRAE Design Manual for Hospitals and Clinics (First Edition)

    WHO = World Health Organization

     

    ASHRAE PD = ASHRAE Position Document on Infectious Aerosols

    FGI = Facility Guidelines Institute

     

    Term Definition Source
    Aerosol generating procedure (AGP) Procedures that are likely to induce coughing. Procedures that are believed to generate aerosols and droplets as a source of respiratory pathogens include positive pressure ventilation (bi-level positive airway pressure [BiPAP] and continuous positive airway pressure [CPAP]), endotracheal intubation, airway suction, high-frequency oscillatory ventilation, tracheostomy, chest physiotherapy, nebulizer treatment, sputum induction, and bronchoscopy. AGPs should ideally take place in an airborne infection isolation room (AIIR). CDC
    Aerosol, infectious An infectious aerosol is a system of liquid or solid particles uniformly distributed in a finely divided state through a gas, usually air. (They are small and buoyant enough to behave much like a gas yet they can be filtered out of the gas.) ASHRAE PD
    Aerosol, Short-range transmission Transmitting disease by inhalation of aerosols near the source. The distance for this transmission has not been studied beyond two meters. CIDRAP
    Age of Air The time that has elapsed after the air enters a space (at any given point.) DMHC
    Air change rate Airflow in volume units per hour divided by the building space volume in identical volume units (normally expressed in air changes per hour [ACH or ACPH]) DMHC
    Air irritant A particle or volatile chemical in air that causes physiological response when in contact with mucosa in the eye, nose, or throat. DMHC
    Air volume migration The volume of air that is exchanged during room entry/exit (through a door-way between a room and the area beyond its door) DMHC
    Air, exhaust Air removed from a space and discharged outside the building by mechanical or natural ventilation systems. DMHC
    Air, makeup Any combination of outdoor and transfer air intended to replace exhaust air and exfiltration. DMHC
    Air, outdoor (1) Air outside a building or taken from the outdoors and not previously circulated through the system;
    (2) Ambient air that enters a building through a ventilation system, through intentional openings for natural ventilation, or by infiltration.
    DMHC
    Air, recirculated Air removed from a space and reused as supply air. DMHC
    Air, supply Air delivered by mechanical or natural ventilation to a space that is composed of any combination of outdoor air, recirculated air, or transfer air. DMHC
    Air, transfer Air moved from one indoor space to another. DMHC
    Airborne droplet nuclei Small-particle residue (5 µm or smaller) of evaporated droplets containing microorganisms that remain suspended in air and can be dispersed widely by air currents with a room or over a long distance. DMHC
    Airborne infection isolation room (AIIR) A room designed with negative pressurization to protect patients and people outside the room from the spread of microorganisms (transmitted airborne droplet nuclei) that infect the patient inside the room. DMHC
    Airborne infectious agent An airborne particle that can cause an infection. DMHC
    Airborne pathogen An airborne particle that can cause disease. DMHC
    Airborne transmission Airborne transmission is defined as "dissemination of either airborne droplet nuclei or small particles in the respirable size range containing infectious agents that remain infective over time and distance." An important requirement of airborne transmission is that it can occur only at a long distance from the source, according to the CDC. CIDRAP
    Air-cleaning system A device or combination of devices used to reduce the concentration of airborne contaminants, such as microorganisms, dust, fumes, respirable particles, other particulate matter, gases and/or vapors in air. Related term: HEPA Filter. DMHC
    Anteroom A room separating an isolation room from a corridor. DMHC
    Bay (patient) A space for human occupancy with one hard wall at the headwall and three soft walls. FGI
    Bioaerosol Particles or droplets suspended in air that consist of or contain biological matter such as bacteria, pollens, fungi, skin flakes, and viruses. DMHC
    Building air infiltration Uncontrolled inward leakage of air (that may contain entrained water vapor) through cracks and interstices in any building element and around windows and doors of a building, caused by the pressure effects of wind or the effect of differences in the indoor and outdoor air density. DMHC
    CADR Clean Air Delivery Rate which is the combined effect of actually how much air is moved through the filter and the filter efficiency. AHAM AC-1
    Community acquired infection An infection present or incubating in a patient upon admission to a hospital (or who subsequently shelters in place outside the hospital). DMHC
    Contaminant or Pollutant Any impurity, any material of an extraneous nature, associated with a chemical, a pharmaceutical preparation, a phuysiologic principle, or an infectious agent. DMHC
    Contaminant, airborne An unwanted airborne constituent that may reduce the acceptability of air. DMHC
    Contamination The act of contaminating, especially the introduction of disease germs or infectious material into or on normally sterile objects. DMHC
    COVID-19 COVID-19 is the short name for “coronavirus disease 2019" WHO
    Cubicle A space intended for human occupancy that has at least one opening and no door and is enclosed on three sides with full height or partial height partitions. FGI
    Droplet transmission Droplet transmission is defined as "respiratory droplets carrying infectious pathogens that transmit infection when they travel directly from the respiratory tract of the infectious individual to susceptible mucosal surfaces of the recipient, generally over short distances, necessitating facial protection." Close contact involves hand transfer of surface contamination to mouth, nose or eyes, hand washing and gloves being common controls. CIDRAP
    Epidemiology Study of the distribution and determinants of disease. DMHC
    HEPA filter (or absolute filter)  High efficiency particle air filter with an efficiency of 99.97% removal of particulates larger than 0.30 microns. DMHC
    Hospital Acquired Infection (HAI) See Nosocomial infection.
    Intensive care rooms (ICU)(also critical care rooms CCU) Rooms in which the level of patient care and electronic monitoring of patients are greatly increased over conventional patient rooms. FGI
    MERV Minimum Efficiency Reporting Value: The fraction of particles removed from air passing through a filter is termed “filter efficiency” ASHRAE 52.2-2017
    Nosocomial infection (or Hospital Acquired Infection [HAI]) An infection that is acquired in a hospital and that was not present or incubating upon admission. DMHC
    Occupationally acquired infection An infection acquired while working in a medical care setting. DMHC
    Opportunistic organism An ordinarily non-infectious agent that becomes infectious in an immunocompromised host. (any novel organism, especially aerosolized respiratory viruses for which there is no vaccine or herd immunity becomes an opportunistic organism.) DMHC
    Pneumonia Inflammation of lung tissue. DMHC
    PPE Personal Preotective Equipment is equipment worn to minimize exposure to hazards that cause serious workplace injuries and illnesses. Occupational Safety and Health Administration, PPE
    Pressurization A difference in pressure between a space and a reference pressure. DMHC
    Room A space enclosed by hard walls and having a door. FGI
    SARS-CoV-2 Severe Acute Respiratory Syndrome CoronaVirus 2 International Committee on Taxonomy of Viruses (ICTV)
    UV Ultraviolet irradiation. DMHC
    UVGI Ultraviolet germicidal irradiation. DMHC
    Ventilation A process of supplying air to or removing air from a space for the purpose of controlling air contaminant levels, humidity, or temperature within the space. Such air may or may not have been conditioned. DMHC
    Ventilation effectiveness The ability of a system to remove contaminants generated by a source in a room. DMHC
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