Indoor Air Quality Considerations

Cleaning for Health originally centered around sanitizing surfaces and touchpoints, but now has an increased focus on cleaning the air your breath based on new guidelines from local and national governments about airborne transmission.

It has been found that air displaced by HVAC systems may contribute to the spread of the virus. There are several recommendations that our experts have put forth.

1. Enhanced Filtration

HVAC filtrations systems need to be fully assessed and upgraded to the COVID-19 recommended MERV-13 filter where possible and applicable.

2. Dilution Ventilation

Studies show that by diluting indoor air with fresher outdoor air, we can mitigate the spread of viruses and improve the overall indoor air quality. This can be accomplished by using a cloud-based Building Automation System that is programmed to utilize HVAC equipment for dilution ventilation. Using cloud access, it allows the user to toggle between ventilation modes to optimize the balance between ventilation and energy consumption.

3. Air Purification & Surface Conditioning

Ultraviolet (UV) lights can be installed within the HVAC systems and indoor space which sanitizes the coil surface to purify indoor air.

4. Occupancy Management

Use technology that can detect if people in a building are wearing masks, have elevated surface body temperature and can count the number of people in a specific area to ensure physical distancing and space requirements.

HVAC Preparation Steps to take when re-occupying a building

As we have continued to move forward during the COVID-19 pandemic we have experienced and will continue to experience a state of flux when it comes to buildings closing and re-opening. These guidelines are included by GDI and Ainsworth to help with any subsequent building re-opening HVAC considerations that may be necessary.

When occupants transition to work-from-home arrangements, the following can occur:

  • A decline in the operational requirement of technical systems
  • Seasonal “shoulder periods” causing low usage
  • Missing Spring/Summer start-up routines

Operational resiliency and health and safety shall be paramount as you prepare your facility for re-entry. Each building owner, manager, operations team and their various technical service providers should discuss and agree what activities constitute the most appropriate facility re-start procedure. Facility use, design, age, types of systems, any known issues, and level of ongoing maintenance since building shut down are key to know.

When re-opening, we urge owners and managers to:

  • Implement a simple re-start plan for each technical area
  • Asses the physical condition and operation of equipment and services
  • Have service providers conduct a more robust level of preventative and predictive maintenance routines
  • Ensure all systems are performing at a high level

Scope of Work Modification

Based on your frequency of cleaning determinations, you should modify your scope of work. This includes:

  • Contacting your service provider to involve them in planning
  • Directing scope based on “risk and resources”
  • Applying a resource calculation to ensure frequency of cleaning is feasible
  • Setting aside resources appropriately for what jobs you expect to be done

Stage 1

Stage 1 involves cleaning and sanitizing in one step

  • If the surface is dirty, refold cloth and wet wipe again after cleaning to ensure proper application of disinfectant
  • Always ensure that the cloth is “wet wiping” the surface so that the disinfectant contacts surface properly. Re-soak as necessary for proper coverage.
  • For electronics that are sensitive to moisture, the rag should be moist and not dripping with chemical solution
  • Allow surfaces to air dry, do not manually dry.

Stage 2

The main difference with a stage 2 response is that the surfaces undergo a two-step disinfection process

  • Stage 2 responses typically apply when there is indirect exposure at the worksite e.g. a co-worker has a symptomatic family member and attended the worksite.
  • Stage 2 responses are for small spaces. If the space is large, or if there is a confirmed case, a stage 3 response is preferable.
  • When disinfecting, apply the chemicals to remain wet for the contact time required for the chemical.
  • This means that after the one step clean + sanitizing, apply the disinfectant again onto non-porous surfaces generously so that it can remain wet for a longer period
  • Continue to other areas while the treated area remains wet
  • Return to wet areas and remove excess moisture, or allow to air dry if there is no urgency to reopen the facility

Stage 3

The main difference with a stage 3 response is the secondary application of chemical with specialized equipment and PPE revisions. Stage 3 responses typically apply when there is a confirmed case. When we don’t know what that person was in contact with or where droplets landed we target as many accessible areas as possible.

  1. Supervisor screens for symptomatic staff and excludes them from cleaning operations
  2. Orientation meeting should be included– the order of operations may change after understanding the site layout
  3. Supervisor does a Pre-walk Evaluation (in full PPE gear).
    – Patrols affected zone to assign and plan work function.
    – Identifies cleanable areas and omits/isolates sensitive equipment that cannot be subject to moisture
  4. Sequential sanitizing of touch points and known/affected area
    – Start from the least contaminated area to most contaminated (alternatively use separate material).
    – Damp wipe surfaces with disinfectant and force to apply friction and remove dust, debris, soiling, biofilms etc.
    – Where practical, move and sanitize items such as keyboards, mice, phones etc.
    – You cannot sanitize paper, or sensitive items, if possible, remove/move them.
  5. Secondary treatment with disinfectant.
    – Depending on the size of the “affected zone” use an electrostatic sprayer or alternative method to coat the surface with disinfectant solution.
    – Application and effectiveness will be subject to “contact time”/“Dwell Time”.
    – Markers help with efficiency but sometimes will not adhere to a wet surface so apply to floor instead.
  • Mechanical Systems  
    • Chilled/condenser water: open/closed loops (cooling towers) 
    • All Ventilation and (booster) pumping systems 
    • Discuss staged cleaning of ventilation ductwork 
    • Evaporators and evaporators pans 
    • Discuss cleaning and sanitization of supply and return grills  
  • Building Automation 
  • Electrical Systems 
  • Water, Sanitary Systems, Traps, Sumps 
  • Water features  
  • Elevating Devices  
  • Potable water: flush faucets  
  • Fire Life Safety Systems  

Fan Section 

  1. Check Filters; change and date if not acceptable 
  2. Clean and sanitize evaporator coil & drain pan 
  3. Check if fans have turned on and air is moving in and out of building 
  4. Inspect motor, pulleys, belts, blower wheel and bearings 
  5. Inspect dampers (outside and return), which help control fresh air to the building 
  6. Check overall building pressure and critical spaces to make sure they are positive 


  1. Inspect wiring, operational and safety controls, disconnects and fuses
  2. Inspect and set thermostat or EMS
  3. Check that the devices and sensors are within an acceptable calibration for controlling space comfort and ventilation 
  4. Check if alarms and alerts are set up and their communication path is correct i.e. it is notifying the right person. 


  1. Verify cooling performance; check the delta’s and if out of range, check if the refrigerant is adequately changed 
  2. Inspect and clean condenser coil with an approved cleaning solution 
  3. Inspect economizer, compressor, condenser fan, and blade 
  4. Check coil leaving air temperatures to ensure the system is providing dehumidification 


  1. Inspect and clean burners/heat exchanger 
  2. Inspect hot gas bypass, ignition and safety controls 
  3. Inspect operational controls/valves 
  4. Verify fuel source is on and available 

Building systems should be started methodically to prevent load shed from a simultaneous start

Depending on length of time equipment has been inactive, systems should be allowed to run for a period with careful observation to ensure valves, switches, seals etc. are operating correctly 

Building employees responsible for assessing the physical structure and building systems must be licensed or certified for their activities and should refer to all authority having jurisdictions.     

MERV Filter Description List

Summary of Considerations