Compiled by Eamonn Ryan from the 3rd SAIRAC Johannesburg Tech Talk online presentation by Edward Erasmus on the topic ‘Guided Approach to Applying UV-C to Mechanical Ventilation Systems’. This is an extension of the summary published in RACA August, and is Part 5 of a six-part series.

It’s essential to assess the building layout, HVAC system specifications, and air flow characteristics.

It’s essential to assess the building layout, HVAC system specifications, and air flow characteristics. Image by Freepik

Continued from part 4…

Edward Erasmus, represents Sani UV-C, a company that specialises in UV-C application used across various applications including cold rooms, vehicle transportation, HVAC systems, and water systems.

Q: Could you show us a typical UV installation, including the lamp locations and their dimensions? Also, can you provide details on the wattage of these lamps? Do they target specific bacteria or cover a broad range?

A: Absolutely, let me break it down for you.

Installation overview:

  • Application specificity: Each installation is unique. It’s essential to assess the building layout, HVAC system specifications, and air flow characteristics. For instance, knowing the coil area dimensions and velocity helps determine the number of UV lamps required.
  • Standard fixtures: We generally use fixtures that are either 700 mm or 1.7 meters long. These come with an irradiance area suitable for various applications.

UV lamp specifications:

  • Wattage: The standard lamps range between 100 watts and 150 watts. We use reputable brands like Philips and Osram to ensure reliability and accessibility.
  • Coverage: For example, a meter by 500 mm duct typically requires less than 100 watts, but we often add an extra 10% wattage to account for factors like dust accumulation and lamp aging. This ensures continuous effectiveness.
  • Longevity: Our lamps are designed to maintain UVC output for around 9 000 hours. While some lamps are engineered to burn out at peak performance, our design philosophy prioritizes sustained irradiance without compromising longevity.

Pathogen targeting:

  • Broad-spectrum effectiveness: UVC lamps are effective against a wide range of pathogens. While specific pathogens may require tailored solutions, our standard approach uses Tuberculosis (TB) as the benchmark due to its high resistance. If the system can handle TB, it can effectively neutralize most common indoor pathogens, including those with lower resistance like Covid-19.
  • Custom pathogen targeting: In cases involving specific or unusually resistant pathogens (e.g., fungi or yeast near breweries or golf courses), we conduct a detailed analysis. This involves looking at D90 tables to determine the required dosage of irradiance to effectively neutralize the specific pathogen.

Practical examples:

  • Typical setup: For a standard air duct of 1 meter by 500 mm, you’d use a 100-watt lamp, providing adequate coverage for a velocity of 1 cubic meter per second. This setup ensures thorough disinfection for over 9 000 hours.
  • Adaptability: Depending on the building’s function—be it a food processing facility, an office, or a healthcare setting—knowing the primary contaminants allows us to adjust the UV installation for optimal performance.

Continue to part 6…