Some of the highest-risk contamination is invisible — until you know how to look.
Twenty years of forensic science expertise, applied to hospitals, hospitality, secure facilities, and any environment where cleanliness matters — not just how clean it looks.
Forensic IPC provides expert advice to organisations interested in using forensic light technology to create a cleaner environment. It is led by Dr Sarah Fieldhouse, PhD in Forensic Science, with over 20 years of forensic experience and a passion for innovation, now applying her knowledge to healthcare through work with the NHS. Sarah works collaboratively with clinical infection prevention and facilities management teams, policy makers, and microbiologists, whose input and expertise are essential to ensuring the work is constructive and meaningful.
Sarah has worked as an Associate Professor of Forensic Science, dedicated to research and teaching generations of forensic scientists, as well as providing consultancy for police forces and acting as an expert witness.
Sarah's aim is to bring the same standard of rigour and evidence to Forensic IPC — bringing forensic light technology into cleaning practice with integrity.
Forensic Light Technology
How clean is clean?
Forensic light reveals contamination that visual inspection alone cannot detect — here's what that looks like in practice.
A genuine public toilet presents as visually clean under white light. Under a forensic light source, multiple surfaces reveal contamination invisible to the naked eye moments before.
Cleanliness in most environments is assessed by visual inspection, but this method is limited by factors such as visual acuity, lighting conditions, and the subjective judgement of the person carrying out the check. As you can see in the video, it is not uncommon to be surrounded by invisible matter, much of which is likely harmless, but some can be hazardous and contribute to the spread of infection.
Forensic scientists meticulously search for substances that are invisible to the naked eye using specialised light sources that cause many common surface contaminants, including body fluids, to glow (fluoresce), and therefore it is possible to use these devices to screen environments for invisible substances — hence the application to cleaning.
They're called forensic light sources here because their specification matches those used in forensic practice, not because their use is exclusive to it. Unlike the low-power UV devices used with fluorescent gel in hand hygiene training and to assess areas that have or have not been cleaned, forensic-grade devices operate at higher intensity across a wider wavelength range, detecting more substances with no pre-treatment required. They're simple to use, portable, and give immediate results — ideal for physical cleaning checks, cleaning auditing, or training your teams. This is the principle behind Smart Cleaning.
Try it yourself
Move the slider to see this unedited hospital bed control panel under white light, UV, blue light/yellow filter, and green light/red filter.
Physical matter you can see is physical matter you can remove
Effective cleaning underpins Infection Prevention and Control practice. Cleaning teams work hard to remove physical matter, such as dirt, debris, and bioburden (the organic material left behind by human contact). Without thorough physical cleaning, disinfectants cannot work effectively as the physical matter shields microorganisms from contact with the disinfectant.
Bioburden, and other hazardous contamination, such as biofilms, can be persistent and invisible to the naked eye. Consequently, surfaces can pass visual inspections of cleanliness, but despite cleaning, persistent physical matter, difficult to clean areas, and damaged or worn surfaces are often where bioburden gets trapped and can remain long after that surface has been wiped or sprayed and treated as clean.
Forensic Light Sources can show you where this is happening — not adding to the cleaning process, but empowering teams to focus on areas that need further cleaning using a rigorous and evidence-based method.
White light
UV light
Cleaned, under UV
What gets missed
Six IPC-relevant contaminants forensic light reveals
Urine
Dried urine fluoresces under the correct light, even when no visible trace remains.
Left undetected: preventable infection risk, particularly UTIs, for anyone who comes into contact with the surface.
Saliva
Saliva dries without visible trace, yet it fluoresces under the correct light.
Left undetected: a route for transmitting respiratory and other infections between people sharing a space.
Limescale build-up
Limescale itself does not fluoresce, but its rough, porous surface anchors biofilm and organic residue, which often do — making persistent limescale a visual indicator of accumulation beneath the surface. This sink had already been cleaned, yet the ring around the plughole still fluoresces brightly under forensic light.
Left undetected: an ongoing biofilm reservoir that routine cleaning cannot fully remove.
Food and drink residue
Many foods and drinks contain naturally fluorescent components. Vitamin B2 (riboflavin), present in milk and many other foods, fluoresces under the correct light, as does quinine, found in tonic water.
Left undetected: a growth reservoir for microorganisms wherever food is prepared or consumed.
Faecal matter
Faecal residue fluoresces under the correct light, even in trace amounts, due to porphyrins produced partly through the breakdown of digested matter by gut bacteria. It can harbour pathogens including C. difficile and norovirus.
Left undetected: direct risk of outbreak-level infection transmission within a facility.
Contact Residue
Contact residue is the trace left on a surface when touched, from gloved or ungloved hands — sweat, metabolites, and contaminants such as oily residue and food. Where sufficient fluorescent matter is present, it fluoresces under the correct light, and accumulates on high-touch surfaces such as door handles, rails, and shared equipment.
Left undetected: a direct route for cross-contamination from hand to surface to person.
Gallery
Genuine examples of physical matter on visually clean surfaces
Mattress
Overbed table
Overbed table
Toilet
Patient call bell
Clip
Microbiological Analysis
Invisible, but not harmless
It's not uncommon to find large amounts of invisible matter on a surface, and most of it is entirely harmless — but as these two examples show, that isn't always the case. Fluorescent physical matter sometimes contains pathogenic bacteria. Here are two examples where the fluorescent matter was analysed using Matrix Assisted Laser Desorption Ionisation (Time-of-Flight) Spectroscopy (the industry standard method).
An important caveat of this method is that not all substances fluoresce, or exist in sufficient quantities to fluoresce. By removing fluorescent physical matter, you are removing physical matter that may include bioburden, reducing overall contamination on a surface. These results also reflect what was present on the surface at the time of inspection, rather than an ongoing guarantee of cleanliness.
Hospital Commode
Fluorescent physical matter contained Lelliottia amnigena, a rare, opportunistic environmental bacterium that causes urinary tract or wound infections in individuals with compromised immune systems.
Hospital Wheelchair
Fluorescent physical matter contained Staphylococcus aureus, bacteria that usually lives harmlessly on human skin but carries an infection risk if it enters the body through cuts, scrapes, or medical devices, leading to conditions such as pneumonia, bloodstream sepsis, bone infections, or endocarditis in vulnerable people.
Forensic IPC can advise on whether and how forensic light technology might support environmental cleanliness in a range of sectors, including healthcare, care homes, education, hospitality, veterinary, dental, labs, and public buildings. This may include advice on the specification of forensic light sources and their suitability in your environment, or supporting you to develop Standard Operating Procedures.
Forensic Surface Examination
Regular or one-off independent forensic light inspections to reveal hidden physical matter, staining, and surface damage.
Surface mapping to pinpoint contamination hotspots and guide targeted cleaning action.
Smarter Cleaning Advice
Evidence-based assessments of cleaning methods using forensic light technology to identify gaps or missed areas with constructive, evidence-based feedback and support for staff.
Incident and Deep Clean Support
Post-incident surface investigations using forensic light technology (plus optional ATP analysis) and targeted, evidence-based advice on cleaning remediation.
Verification of post-incident or deep-clean effectiveness.
Forensic Light Source Training
For practical, hands-on training, including immersive VR, delivered through the official Forensic IPC training partner organisation.
