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Winter challenges: heating and air filtration

Business | December 1, 2020 | By:

How to keep tents, buildings, warehouses and other structures warm and dry during the COVID-19 pandemic.

by Daryl Benz

Heating tents and other temporary structures is always a challenge whenever the weather gets colder. But factor in the pressures of combatting COVID-19 and you have a potentially complex situation on your hands.

The Centers for Disease Control (CDC) and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) have recommended three core measures to improve air quality in buildings and structures of all kinds, whether permanent or temporary. You will need to focus on bringing in more fresh air from outside, increasing your circulation to around four to six air changes per hour, and introducing extra mechanical air filtration measures. All of these are achievable, but when you combine them with seasonal heating requirements, you’ll need a bit of creative planning to get it right.

Warm air concerns

Let’s say you decide to use an indirect heater to blow warm air into your tent, for example. This helps you to get more fresh air in, so that’s one box ticked. But it also causes a number of problems.

First, warming up fresh air takes more energy than reheating return air through an HVAC unit, which can make it very expensive to heat. You also need to be very careful about where you’re actually sourcing the outside air from. The aim is to bring clean, fresh air into the building, so make sure you aren’t drawing it from a source point near a crowd, a dusty field or a dumpster.

Second, filtration of the air on an indirect system can be problematic. You can’t simply put an air filter on the supply side to clean the hot air as it’s fed into the tent because it’s too hot and will melt or burn. Also, most indirect units have no means for adding a filter to the heater’s return, so you can’t mechanically filter the air, according to industry guidelines. And, to make things worse, you’re blasting that hot, fresh air right through the tent to get it to the colder areas. If there are any airborne contaminants or viruses inside your tent, these will be circulated, too.

 Meanwhile, direct-fire heaters are notoriously bad for releasing moisture into the air, and humidity is a big problem when you’re trying to control the spread of disease. Damp air is a real issue when you’re trying to avoid misting over plastic masks, face shields, dividers and other personal protective equipment (PPE).


How should you tackle these challenges? One simple improvement is to use a hydronic heating system. Hydronic heaters run hot water through pipes along the outside walls of a structure, and use air handlers to distribute a dry heat. More importantly, fresh air in the interior can be fed safely through an air handler with hospital-grade, MERV-13 filters.

To meet increasingly stringent safety standards, these can be further combined with HEPA filters to clean the air to a hospital-like spec. However, high current demand for HEPA filters means unfeasibly long lead times for many companies. Luckily, UVC lights offer an excellent alternative. By installing these in the return air compartment of heaters or air conditioners, you can sterilize the air as it passes through, preventing airborne bacteria or viruses from reproducing. Adding air scrubbers to the mix is another excellent safety-boosting measure to help increase air changes and clean the air, improving internal air quality.  

It’s important to keep in mind that, while these kinds of interventions vastly improve air quality and safety, people working inside still need to wear the right PPE and observe social distancing rules and other COVID-19 regulations. The “new normal” has also created a new job title on many sites—COVID-19 Compliance Officers—so it’s crucial that you work closely with these people to ensure you’ve covered all of your bases. For this reason, it is imperative to select an HVAC vendor who keeps up with all local, regional and federal rules regarding air quality and COVID-19 guidelines. Your vendor should offer site-specific engineering design services rather than just giving you the kit and leaving it to you.

The show will go on

Will these additional pressures require extra planning and resources? Yes. Does this mean you will inevitably need to cancel events, projects and developments? No. With the right preparation, you will be able to heat tents and other structures safely and effectively. In the past few months,
my team has used these kinds of temporary heating and air filtration technologies to get the conditions right for a major boat show in Florida and numerous medical tents throughout North America. We’re also working with Amazon and Apple Studios to make tents, warehouses and studios safe places so that the film industry can start shooting movies again. 

The challenges created by this pandemic are enormous, but they’re surmountable. With the right attitude—and technology—the show can and will go on. 

Daryl Benz is a temporary HVAC expert at Aggreko, a world-leading provider of mobile modular power, temperature control and energy services.

SIDEBAR: Three steps for improved air quality 

The CDC and ASHRAE (the global society for HVAC air quality and sustainability) have issued the following guidelines to improve the air quality in enclosures:

  • Increase the percentage of outdoor air that circulates into the system.
  • Increase ventilation rates, or “air changes” per hour.
  • Introduce mechanical support for return air systems, such as high quality filters, UV lighting and air scrubbers. 

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