How HVAC prevents you from getting sick

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How HVAC prevents you from getting sick
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How HVAC prevents you from getting sick

– Jaco Heinen, 25/04/19

The room smelled of bacon, dried sweat and dusty old things. There was only one seat, at a table in the far back of the room. Three men dressed in orange coveralls were sipping their coffee while a guy with a dark beard coughed softly into his hand. “Two weeks before we reach port,” one of the men said. Suddenly the bearded guy sneezed over the table. “Sorry,” he said. “Caught a cold during our last visit on shore.”

In the air

There is much more risk of getting sick in a crowded environment like a boat. A sneeze or a cough expels thousands of miniscule droplets filled with bacteria and microorganisms into the air. These suspended particles quickly spread through the room, not unlike an aerosol from a spray can. How can you prevent the crew from getting infected? A proper HVAC system goes a long way. A well-designed installation deploys the following to prevent bacteria from spreading:

  • Ventilation
  • UV light
  • Relative humidity.

Ventilation improves air quality

The simplest way to get rid of viruses and bacteria is ventilation. Imagine opening a window and letting the old damp air out and fresh outside air in. A good HVAC system ensures that there is always sufficient fresh air inside. ISO 7547 specifies a minimum of 0.008 m³ per second per person of outdoor air. This is equivalent to roughly 30 m³ per hour per person.

Although fresh outside air keeps bacteria from spreading, there is also a downside. Outside air needs to be treated by an air-handling unit – and the more air, the bigger the unit. That in turn requires recirculation in order to save on energy and installation costs. It’s important to strike the right balance between recirculation and fresh air.

Ultraviolet filtering

Placing UV lights in the air-handling unit filters the air that enters the unit. UV light has short wavelengths which are harmful to microorganisms, breaking their molecular bonds and eventually killing or disabling them. This cleanses recirculated air from bacteria and viruses.

Using relative humidity to prevent disease

Keeping the relative humidity at a minimum of 40% has an enormous impact on the spread of bacteria. Increased moisture makes the suspended particles containing microorganisms heavier, causing them to stick to the floor and walls and preventing them from spreading through a space. It’s far more difficult for bacteria to survive in a humid environment.

Dry air in turn has a negative effect on human resilience. It leaches moisture from mouth and nose, which normally traps microorganisms and prevents you from getting sick. Without the moisture, you are more susceptible to colds and the flu, for instance. Moreover, skin that gets dry and cracked is more vulnerable to bacteria. And remember that keeping relative humidity between 40% and 60% doesn’t just prevents sickness: it also keeps your skin smooth and better looking.

Jaco Heinen | Service & Maintenance Manager

Jaco Heinen has been working at Heinen & Hopman for over eight years. He became the Service & Maintenance manager four years ago and manages the service contracts for maritime HVAC installations worldwide.