**August 20, 2020 Update** A more detailed version of this information has been published at the College Covid 19 Site.

I had a really informative meeting with Susan Lindemann, Director of Facilities Management, about the ventilation systems in our classroom buildings and steps being taken to prepare for on-campus classes this fall. The College is following the Covid19 guidelines of the  American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), Here are five things I learned

1. Fresh Air
2. Windows — please leave them closed.
3. Air handling is different than temperature/humidity control, but those are related
4. Different classroom buildings have different needs
5. Portable air purifier units

1. Dilution is the Solution to Pollution

The key idea is to dilute indoor air, and any infectious material in that air, with fresh air from outdoors. The air handling systems in classroom buildings at K have the capability to do exactly that with large outside air intake devices on each building. In fact, that was the case before Covid19 too. In the past, the mix of recirculated air and fresh outside air was achieved automatically by instruments that detect and maintain carbon dioxide levels in the building at healthy levels while improving energy efficiency by recycling some of the indoor air that has already been heated or cooled.

As we turn our attention to preventing possible spread of Covid19 by particles and aerosols in the indoor air, these systems are being reconfigured to increase the amount of outside air being brought indoors. This, together with the lower building occupancy associated with the College’s distancing and de-densifying plan, increases the effective dilution ventilation per person.

2. The Unintuitive Thing About Windows — Leave Them Closed.

In my house, the easiest way to dilute the inside air with fresh air from outside is to open a window. The situation in classroom buildings is different: The systems that detect and control the amount of fresh outside air in the building are tied directly to the outside air intake location in each building and not to any given room. Opening a window in one room disrupts the fresh air sensing equipment for the whole building, resulting in less fresh outside air being brought into the other rooms in the building.

3. What you feel in the air: Air Handling and Temperature Control are Different Things

The aspect of the building’s indoor environment we are most aware of is the temperature and humidity. The environmental control systems in the classroom buildings at K maintain a comfortable interior environment by two separate processes: air handling and hydronics.

Air handling is what we’ve been talking about in the points above. The hydronic system involves moving air past coils filled with heated or chilled liquid. That heating and chilling happens in the boiler/chiller plant at the bottom of Academy Street, with the hydronic liquid passing through underground pipes to the classroom buildings.

The air handling systems will be configured to bring more outside air into the mix to achieve greater dilution in each building, but of course we know that for most of the academic year in Kalamazoo, that outside air is cold! The amount of fresh outside air that can be included in the air handling mix will need to be balanced with the capacity of each building’s hydronic system to maintain a comfortable and safe temperature.

4. Different Buildings, Different Systems

What about my building? Here are some things to know:

• Dow Science building, because of its design for preventing airborne health hazards from chemistry and biology labs, has always included 100% fresh outside air in the air handling mix. There is no recirculation of interior air at all. The extra-high capacity hydronic system designed for that building maintains the indoor environment at comfortable temperature and humidity.
• Olds-Upton Hall has an air-handling system which is adequate for its traditional usage, as well as high dilution with greater proportion of fresh outside air discussed here. The hydronic system in OU is undersized for that purpose however. For that reason, it is possible that temperatures in OU will be less comfortable this year. To help maintain interior comfort, portable electrostatic air purifier units are planned for classroom spaces in OU, allowing for fresh air levels to be better balanced with the capacity of the hydronic system while at the same time actively reducing the concentration of any infectious material in the air.
• Dewing Hall is a tale of two zones. The air handling unit for the 3rd floor is not configurable to bring higher amounts of fresh outside air into the mix. For that reason, portable electrostatic air purifiers are planned for any classroom space in use on Dewing 3rd floor. The other levels of Dewing hall have a separate air handling system which allows for the greater dilution with outside air we’ve been discussing here.
• Light Fine Arts has generally adequate air handling capacity for including greater dilution of outside air. The special purpose uses of many spaces in LFA — for activities that traditionally bring large groups together in close contact while singing, acting, playing wind instruments, etc — bring with it special considerations.
• Upjohn Library Commons has generally adequate air handling capacity for including greater dilution of outside air. The need for special climate control in the rare book room brings extra considerations into play.

5. Portable Air Purifier Units

A lot of portable electrostatic air purifier units are on order now for use in classroom spaces in Dewing and OU, with deliveries scheduled to begin in the first few weeks of the term. As with other high-demand items — remember that every other higher education institution is making similar orders — the delivery dates are likely to change. These units are rated to handle large rooms from 1500 to 3000 square feet (1500 square feet is 30×50). We won’t know until they arrive how much sound they generate and the resulting impact on classroom acoustics.