Ultraviolet Solutions FAQ

Ultraviolet germicidal irradiation (UVGI) is the application of UVC for disinfection purposes.

At a wavelength of 254 nanometres, UVC breaks the elemental bonds in organic matter, firstly preventing reproduction and eventually leading to cell death.

UVGI was used to help eradicate tuberculosis in the early 1900s and today is widely used in healthcare and for disinfecting aquariums and drinking water. In food processing UVGI is used to pasteurise juices and milk, to prolong the shelf life of soft fruit and vegetables and to protect meat when hanging to mature, reducing spoilage by bacterial contamination.

UVGI has seen widespread use in HVAC system air handling units. Properly modelled, a UVGI system replaces manual cleaning by eradicating nearly all elements of the biofilm on the surfaces of cooling coils and drain pans in an AHU, restoring performance as closely to ‘as built’ as possible. The benefits are outlined in detail below.

Filters don’t trap the biofilm on the surfaces of cooling coils and drain pans, they trap particles in the airflow. High-efficiency particulate arrestance (HEPA) filters cannot screen viruses, but they do trap most bacteria so can actually harbour organic and non-organic debris, a potential bio-contamination hazard.

No. Recirculated air contains bio-contaminants from the occupied spaces – the reason for recirculating indoor air is to save energy. However, this compromises the health and wellbeing of the occupants by recirculating contaminated air and bio-contaminants that leach from the biofilm into the air. UVGI disinfects the air every time it passes through the cooling coil, eradicating more than 99% of the bio-contaminants in the recirculated air and increasing the life of filters.

You may not be able to see it, but it’s there. The only way to prove it is by taking samples from the surface of the cooling coil and drain pan.

No. Even if an AHU is cleaned on a regular basis, say weekly, biofilm will begin to build up on the surfaces of the cooling cool and drain pan after cleaning. Manual cleaning can also force inorganic and organic debris into the cooling coil, exacerbating the problem that led to the need for cleaning. With UVGI, the UVC light is reflected off the coil surfaces all the way through the coil and over a period of time will completely eradicate all traces of biofilm.

Biofilm reduces the thermal performance of the cooling coil; 0.006 inches (that’s 150 microns) will degrade performance by about 5%, 0.012 inches (300 microns) by about 10%, 0.024 inches (600 microns) by about 20%, 0.036 inches (900 microns) by about 30% and so on. Reduced thermal performance of the cooling coil increases the work done by fans and chillers to maintain a temperature set point. UVGI restores thermal performance and cooling capacity to ‘as built’.

UVGI can be fitted to both new and existing HVAC systems. UVGI fitted in new AHUs will prevent biofilm from forming, allowing HVAC system performance to remain ‘as built’. Retrofitting UVGI to an existing AHU will eradicate all biofilm and system performance will be returned to ‘as built’.

No, the UVGI system should run continuously. We model the Total Coil Disinfecton System to achieve the desired outcome whilst using the least amount of energy for the lowest cost of ownership.

Yes, providing sensible precautions are used to avoid exposure of eyes and skin. All Total Coil Disinfection (TCD) Systems systems are fitted with a door interlock switch as standard to cut the power to the UVC photonisers when the AHU door is open.

We install a UVGI array, composed of one or more TCD units with UVC photonisers, in close proximity to the air on the side of the cooling coil, permanently eradicating biofilm on the surfaces of the coil and drain pans.

The TCD modelling process takes into account the width, height and depth of the cooling coil, with the outcome based on strict scientific principles and laboratory testing at Gibbns Engineering Group. TCD UVC photonisers are available in two intensities – standard and high. The desired outcome will dictate the number of photonisers, their positioning and whether to install on both the air-on and air-off sides of the coil.

Most UVC photonisers need to be replaced every year (about 9,000 hours) when output is 80% of its original level. TCDUVC photonisers have been designed to maintain 80% of their full output for two years (about 18,000 hours).

Yes, photonisers are similar to fluorescent tubes and will break if mishandled. We offer a Teflon-coated photoniser to encapsulate the standard quartz glass tube in case of damage that leads to fragmentation of the quartz. The coating reduces the output so should only be used where there is a specific requirement.

The TCD UVC photonisers do not produce ozone; they are engineered to produce UVC light at 254 nanometres (nm) for maximum germicidal affect. Ozone is produced at a UVC wavelength of 185nm for grease and odour-control applications.

The costs of manual cleaning are eliminated, energy expenditure is reduced across the whole HVAC system and AHU condensate can be recycled as grey water. Equipment longevity is increased as the load on system components such as fans and chillers is returned to ‘as built’ specification.

UVGI eliminates the need for cleaning chemicals and water, as the condensate in the drain pan can be recycled as grey water. A UVGI system will qualify for BREEAM or LEED points on energy, water and indoor air quality. The TCD system that we model, supply and install does all of the above at the lowest cost of ownership.

UVGI improves indoor air quality by eradicating biofilm from the surfaces of cooling coils and drain pans, reducing absenteeism and increasing productivity. Installing such a system will also make staff feel valued, which in turn increases team morale.

We sample the surface of the cooling coil for contamination and take before and after measurements of airflow and temperature with approved calibrated digital equipment. You will receive a detailed report.

Yes, we can carry out a trial on one AHU to demonstrate the results on your own equipment, based on our initial report. We take measurements of airflow and temperature before and after the 60-day trial period. You will receive a detailed report of our findings and conclusions.

On multiple systems we can tailor a package to suit you, which can involve detailed testing to a pre-defined standard. Our systems are bespoke to each AHU.

The TCD unit is 100% warranted to be free from defects for a period of one year. The UVC photonisers are warranted for two years. Electronic ballasts have a whole-life warranty, provided the photonisers are changed every two years.

Yes, we have other UVC products with specific UVGI applications, including HVAC ducting, kitchens, odour control and washrooms.