Case Study
Sanitising Light Solutions -
Cruise Ship Cabin
The Effect of Our Sanitising Light Solutions on E.coli - Phase 2
Maintaining a balanced microbial load in the environment is essential for supporting the immune system and ensuring the natural interaction between living beings and non-infectious microorganisms. Over-sterilisation, especially in everyday environments, has been shown to weaken the immune system. Guided by this understanding, Our Sanitising Light Solutions prioritise a sanitisation approach that eliminates harmful pathogens like E.coli and SARS-CoV-2 while preserving the effectiveness of the human immune system.
Last month, we produced a case study concerning the efficacy of Our Light Solutions on SARS-CoV-2 and E.coli at the ICGEB Labs in Trieste. This month, we continue this case study with phase 2, where Our Sanitising Light Solutions are installed and tested in a model cruise ship cabin.
Background
This study took place over two practical phases:
Phase 1 involved tests at the ICGEB laboratories in Trieste to evaluate the effectiveness of Our Light Solutions against the human coronavirus SARS-CoV-2 and a specific strain of E. coli.
You can find the article on this phase here: Phase 1
Phase 2 involved testing in the environment through the installation of Our Lights in a model Cruise Ship Cabin installed in the
laboratories of the Faculty of Engineering of the University of Trieste.
The testing during Phase 2 happened over a 24-hour period. The tests were conducted using lights with power 40 times lower than those used during phase 1. This is because the primary goal of the test was to demonstrate the containment of the infectious risk in real conditions during a period of normal use of the cabin during a cruise.
Phase 2 - Materials and Methods
Researchers conduct environmental contamination tests in two steps—before and after installing the lights. Since the environment is a model cabin, they used a hybrid method in which they placed pre-contaminated petri dishes with E. coli around the room.
This test had several limitations. Researchers could not monitor key factors such as temperature and humidity. Additionally, they had no way to prevent other airborne microorganisms from contaminating the petri dishes. In phase 1 lab tests, they used an open flame near the petri dishes to prevent recontamination. However, in this scenario, the presence of flammable materials made this method too hazardous.
Inside the model cabin, researchers distributed 112 petri dishes across seven key locations: Bed 1, Bed 2, Sofa, Floor under Ceiling Light 1, Desk, Mini-bar, and Suspended 25 cm under Ceiling Light 2.
They kept both ceiling lights off during the tests to replicate regular use, while the rest of the lights remained on. However, other objects and furniture blocked the beams from reaching their intended surfaces. Researchers did not consider this an issue, as such obstructions would be typical in a real cruise ship cabin.
As seen in this photo, researchers also included a controlled variable by placing 56 contaminated petri dishes in the same areas, each covered with aluminium foil. This allowed them to measure the direct effect of the Our Lights on microbial growth, comparing it to the results from the exposed dishes. The foil acted as a shield, preventing the devices from affecting those samples, ensuring that any changes in microbial load could be attributed solely to the system’s action. This setup helped to better understand the effectiveness of Our Lights under different conditions.
Phase 2 - Results
Despite the issues mentioned earlier, the number of microbial colonies on the exposed plates at the end of the experiment showed a significant decrease. Starting with an initial population of 1000 CFU/ml, the average reduction was over 70%. The reduction ranged from 51% at the Mini-Bar to 91% at Ceiling Light 2, as shown in the graph here.
To evaluate the results, the tests compared two types of samples: the exposed plates (positive samples) and the unexposed plates (negative samples). Looking at the graph here, it’s clear that only in two cases did the exposed plates have a higher microbial count than the unexposed plates, with an average difference of 15% at the Floor and the Mini-Bar.
Phase 2 - Discussion of Results
In these cases, objects such as furniture in the cabin obstructed the light beams.
Meanwhile, three key facts should be considered when analyzing these results:
1. Real-World Performance
Our Lights are designed to function in real-world environments with actual contamination. However, the model cabin tests used bacteria grown in culture media that promoted rapid replication. In real environments, bacteria grow much more slowly on regular surfaces. Given these controlled conditions, the test results are even more impressive.
2. Bacterial Growth and Light’s Effectiveness
The death rate of E. coli during its rapid growth phase is 0.7 CFU per 1,000 CFU per hour. If the bacteria replicated every 30 minutes, an initial colony of 1,000 CFU would grow to an astonishing 277 quadrillion CFU in 24 hours, even accounting for the natural death rate. These findings highlight how effectively Our Lights can limit bacterial growth, even under real conditions.
3. Impact of the Photoelectric Effect
The control samples exhibited a similar death rate to the test samples, suggesting that aluminium foil used to protect the plates did not prevent colony reduction. Instead, some bacteria died due to the photoelectric effect. This phenomenon occurs when light strikes a metal surface, transferring energy to electrons and emitting photoelectrons. Even low light levels can trigger this effect, as a single photon can instantly interact with an electron.
Conclusion of Results
To keep environments safe and healthy, it’s important to control the microbial load without eliminating all microorganisms, as this can weaken our immune systems. Anglo Nordic follows the idea that a good sanitisation system should manage this balance, protecting against harmful germs while allowing beneficial ones to remain. Unlike chemical disinfectants, which only work when no one is around and lose their effectiveness over time, Our Sanitising Lights provide continuous, passive sanitisation that is safe for both people and the environment.
The tests on Our Lights in a lab and real-world conditions (such as this mock cabin) shows that they work well, even when conditions aren’t perfect. The results showed an average reduction in microbial load of 70%, with some areas seeing up to 91% reduction, which is a great outcome for ensuring hygiene in confined spaces.
So why not talk to us about Our Sanitising Light Solutions as part of our Healthy Buildings range.
If you’d like to find out more about our approach and experience in creating healthy buildings please do get in touch, or check out our other case studies.