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The American Hotel & Lodging Association Safe Stay®  Guidelines provide an overview of measures to assist with indoor air quality measures. In addition to face coverings, physical distancing, and hand hygiene and disinfecting protocols, strong air ventilation and air quality are key for mitigating the spread of COVID-19.

The information outlined here builds off the Safe Stay - Indoor Air Quality Checklist, to provide additional details and insight from Carrier.


Indoor Air Quality Checklist

Indoor Air Quality Checklist – Additional Details


Service  Ventilation 
Filtration Monitoring
Controls Supplemental Air Treatment 





The first step in reducing the of airborne transmission in the building environment is to bring the HVAC system back to its original, commissioned state. ASHRAE suggests that the owner undertake a “tactical commissioning” of their building system to ensure that it is operating per design conditions and current operational strategies. This activity is usually accomplished with the assistance of a licensed and certified commissioning provider, a test and balance company and/or a building automation systems company.1 The results of a tactical commissioning can create substantial energy savings or improvements to indoor air quality (IAQ).

Carrier recommends that hotels…

  • Execute any deferred maintenance tasks on the air handling equipment of the building
    • Wear PPE during any maintenance activity where re-aerosolization may occur.
    • Prioritize maintenance level fixes that could enable higher ventilation or filtration rates, including fan belts, dirty coils, stuck dampers, etc.
  • Conduct a building systems inventory
    • The inventory should include design documentation, and systems information such as fan powers, fan curves, filter efficiencies, system heating and cooling capacity, etc. to inform retrofit opportunities.
  • Retro-commission airside equipment back to the original design intent
    • Include ventilation, pressurization, airflow distribution and optimization, and mechanical filtration.
    • Special attention should be paid to test and balancing of areas with higher transmission risks such as breakrooms, conference rooms, and exhausted bathrooms to ensure appropriate air change rates, pressure relationships, etc.


The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) concludes 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.”2 For building owners and engineers, optimizing these systems generally, and through the adoption of specific air filtration solutions, can effectively reduce the risk of pathogen transmission, improve the health and comfort of occupants, and maintain the profitability and competitiveness of their building operations.

Viruses such as SARS-COV-2 are often found in diffcult to filter "most penetrating particle size" range that requires high efficiency filters to capture. However, the American Society for Microbiology’s (ASM) notes that “viruses are rarely observed as individual particles, but instead are expelled from the body already combined with water, proteins, salts, and other components.” Consequently, the deployment of highly rated MERV and HEPA filters can play a substantial role in capturing particles infected by SARS-CoV-2 and reducing the risk of disease transmission throughout the built environment.

Carrier recommends that hotels…

  • Inspect and change all filters requiring replacement.
  • Inspect filter racks and seal the edges to limit potential bypass.
  • Compare the current filter efficiency levels with the latest relevant regional best practices (e.g., latest version of ASHRAE 62.1) and record the difference.
  • Where current filtration is of lower efficiency than current best practice, install the highest efficiency filtration as the system allows, optimally targeting MERV 13 or better. 


​​​​Outside of system retrofits and equipment replacement, this can be achieved through modifications to the HVAC controls that balance the needs of comfort conditioning, energy consumption, and enhanced ventilation.

Owners and operators should make changes incrementally, document effects carefully and seek input from occupants. Adjusting building and space pressurization is one such example. When increasing outdoor air without adjusting exhaust and relief air systems, doors may not close and occupants may experience excessive noise at entrances and between adjacent spaces. Changes in building pressurization can also affect vertical transportation systems and areas intended to be negatively pressurized, such as commercial kitchens, bathrooms, process areas and custodial areas.

For the duration of SARS-COV-2 community spread, Carrier recommends that hotels…

  • Modify ventilation controls to ensure three air changes of building volume using outside air, or a flush period of about four hours after last occupancy.
  • Disable occupancy-based demand control ventilation (DCV) controls sequences that suppress outside delivery.
    • This includes occupancy counting or CO2 based control logic. 
  • Create an event response purge program to be enabled for three outdoor air changes or four hours after a confirmed infection.

In addition, Carrier recommends that hotels…

  • Add updated control logic to adjust the economizer to supply outside air at the greatest rate possible, consistent with the equipment’s capacity to maintain acceptable temperature and humidity.


Under widespread community spread conditions, ASHRAE “encourages building operators to increase their system’s outdoor air ventilation to reduce the recirculation of air back to the much as the system and or space conditions will allow.”4 Increasing the outdoor air ventilation will increase the dilution and exhaust of indoor environmental contaminants, including viruses.

In meeting this guidance, facility engineers must factor climate, unit capacity and space requirements for temperature and humidity.

For the duration of SARS-COV-2 community spread, Carrier recommends that hotels…

  • Modify their systems to provide the maximum continuous ventilation rate the system can handle without compromising thermal comfort or moisture control.

In addition, Carrier recommends that hotels…

  • Verify the proper operation of all system fans, economizer dampers and zone dampers.
  • Verify that outside air intake and exhaust are free of obstruction.
  • Where system ventilation rates are lower than current best practice (latest version of ASHRAE 62.1), revise minimum ventilation rates upward as close to compliance as possible with current system capacity, taking into account pre-existing rezoning, current terminal unit turndowns, and changes to occupant density that may impact the ventilation rate procedure (VRP) or equivalent calculations.
  • When reenabling DCV sequences following the end of community spread, adjust controls to maintain minimum ventilation rates at levels equal to or greater than ASHRAE 62.1 with a minimum turndown set no lower than the area component of the VRP calculations.


IAQ sensing and system fault detection and diagnostics (FDD) allows for the measurement of temperature, relative humidity, carbon dioxide, volatile organic compounds, filter status and occupancy. Specific to enhanced ventilation strategies, CO₂-based IAQ sensors can indicate that a controlled space is being adequately ventilated and can also generate alerts and alarms in cases where it is not, allowing the building operator to take necessary corrective action.

Additionally, it is important to conduct a one-time IAQ assessment of targeted building spaces in order to understand the building baseline performance. Once a baseline is established, IAQ sensing and monitoring has a point of comparison to identify system underperformance and potential service needs.

Carrier recommends that hotels…

  • Implement best practice fault detection and diagnostics on air handling equipment (latest version of ASHRAE Guideline 36).
    • As possible, extract values from the BMS. Emphasize CO2 and PM2.5 as proxies for HVAC performance to occupant density and aerosol transmission risk.
  • Conduct a one-time IAQ assessment of targeted areas to establish a baseline performance metric, prioritizing areas with higher occupant density or where social distancing may be difficult such a breakrooms, elevator cabs, and frequented common areas.
    • Measurements for temperature, humidity, PM10, P2.5, VOCs, and CO2 are recommended.

Supplemental Air Treatment 

Some HVAC systems and applications will not support increasing ventilation rates or filtration efficiencies to levels recommended for suppression of airborne transmission. In those situations, portable air cleaners with suitable clean air delivery rates (CADR) can be deployed to clean the room air to increase effective air change rate.

To date, ASM reports, “SARS-CoV-2 has been observed in aerosolized particles in a spectrum of sizes including 0.25 to 0.5” microns.3 Consequently, the deployment of highly rated MERV and HEPA filters can play a substantial role in capturing particles infected by SARS-CoV-2 and reducing the risk of disease transmission throughout the built environment. 

For the duration of SARS-COV-2 community spread, Carrier recommends that hotels…

  • Deploy portable filters in areas with higher occupant density or where social distancing may be difficult such as the reception area, lobbies, breakrooms, and frequented common areas targeting a minimum of 15 cfm/occupant CADR, but optimally 30 cfm/occupant CADR.



  1. “ASHRAE Epidemic Task Force, Building Readiness,” May 21, 2020
  2. “Pandemic COVID-19 and Airborne Transmission,” ASHRAE Environmental Health Committee, approved 4/17/20, Web April 23, 2020, https://www.
  3. Leslie Dietz, “Correction for Dietz et al.”, correction made after original publication, 2020, Web May 14, 2020, e00375-20.
  4. ASHRAE Epidemic Task Force,” Web October 27, 2020, 15.

Additional Resources


**Legal Disclaimer
This information is intended solely for the purpose of providing the hotel industry with top line health and safety guidance during the reopening phase of the economy. The information provided is obtained from publicly available sources, including federal agencies and governmental entities, member companies, other leading trade associations and consultants. The information contained in these guidelines is general in nature and should not be considered to be medical, legal, insurance or any other professional advice. In all cases you should consult with professional advisors familiar with your particular factual situation before making any decisions. While we have taken every precaution to ensure that the content of these guidelines is both current and accurate, errors can occur. AHLA and the AHLA Safe Stay Advisory Council and the Stay Safe Partners assume no responsibility or liability for any errors or omissions in the content of these guidelines. The information contained in these guidelines is provided on an “as is” basis with no guarantees of completeness, accuracy, usefulness or timeliness and without any warranties of any kind whatsoever, express or implied. In no event will any of the authors, contributors, administrators or anyone else connected with AHLA or the AHLA Safe Stay Advisory Council, in any way whatsoever, be liable to you, or anyone else, for your use of the information contained in these guidelines, or for any decision(s) made or action(s) taken in reliance upon the information contained in these guidelines, or for any direct, indirect, incidental, special, exemplary, punitive, consequential or other damages whatsoever whether in an action of contract, statute, tort or otherwise, relating to the use of these guidelines.