1. Species evidence crosses borders
A peer-reviewed 2005 study compared mold-specific quantitative PCR results from 11 randomly selected UK homes with 45 typical homes in Ohio. Only 13 of 81 species showed statistically significant concentration differences. The authors concluded that, although the survey was small, typical UK and Ohio home mold profiles appeared broadly similar.
This supports the relevance of species-level PCR evidence across the Atlantic, but it does not make an ERMI score a diagnosis, a complete building assessment or proof of individual causation. Sampling design, dust history, geography, building conditions and the concentration of individual species still matter.
2. United States and New York City
New York City guidance requires relevant owners to correct underlying moisture problems, use safe work practices and leave the work area dry and visibly free of mold, dust and debris. Larger projects in specified buildings require New York State-licensed assessment and remediation workers, and the same licensed person cannot perform both roles.
In July 2026, Mayor Zohran Mamdani's administration proposed stronger enforcement, including possible financial penalties in the Underlying Conditions Program where landlords fail to remediate mold. This is a proposed reform and should not be described as enacted law until its legal status is confirmed.
3. United Kingdom
PAS 64 and BS 12999 provide UK frameworks relevant to damage management, mitigation and recovery. They should be applied according to their scope and current edition, alongside legal duties, risk assessment and competent professional judgement.
Awaab's Law has applied to the English social rented sector since 27 October 2025. Potential emergency hazards must be investigated and relevant safety work completed within 24 hours. Potential significant hazards must be investigated within 10 working days; findings must be given to the tenant within 3 working days after the investigation; relevant safety work generally follows within 5 working days.
Awaab's Law itself does not impose fines. A court may order repairs, compensation and legal costs. Other statutory and regulatory failures may carry financial penalties. Speed is essential, but hurried work without containment, source correction and suitable verification can increase exposure rather than reduce it.
4. IICRC S500 and S520
IICRC S500 addresses professional water-damage restoration and S520 addresses professional mold remediation. Their condition classifications and remediation principles are important building-work tools. They are not medical diagnostic systems.
A “Condition 1” or normal fungal ecology classification should not automatically end every enquiry. The question being answered, sampling limitations and occupant circumstances still matter. Spores, hyphal or biological fragments, microbial volatile organic compounds, cleaning chemicals and other contaminants may require evidence outside a narrow visual or fungal-ecology assessment. Their presence does not by itself prove illness or individual causation.
5. International guidance in the Building Forensics library
A Building Forensics book volume compares mold-removal and treatment guidance from the United States, United Kingdom and Germany. It is used as a comparative resource, not as a substitute for the law, standards or competent advice applicable to a particular location and project.
6. Measurements and climate are not interchangeable
US reports commonly use °F and US customary units; UK and European work commonly uses °C and metric units. A value should never be copied across a report without stating the unit and, where needed, showing the conversion. One easy-to-miss example is humidity ratio: US practice may use gr/lb, meaning grains of moisture per pound of dry air, while metric practice may use g/kg. These are not the same numbers. Airborne concentrations such as µg/m³ answer a different question again.
Climate and building operation also change the investigation. Much of the United States includes strongly cooling-dominated or heating-dominated regions, while many European locations have comparatively temperate, mixed or maritime conditions. Air-conditioning, heating, vapour drive, insulation and seasonal indoor–outdoor differences can therefore move moisture in different directions. Local climate data and the building's actual operating pattern should be used rather than a transatlantic rule of thumb.
7. Exposure routes and life stages
An exposure history may need to consider inhalation, ingestion, skin contact and material carried into the home on clothing, footwear, skin, hair or vehicles. It may also need to consider relevant parental exposure before conception, during pregnancy and after birth. An HSE research report on parental occupational chemical exposures illustrates why route, timing and take-home exposure can matter.
That report concerns occupational chemicals and childhood cancer research. It is not a mould study and does not establish that parental mould exposure caused an illness. It is retained in the supporting knowledge base as evidence for taking a wider, carefully qualified exposure history.
8. About the author
Jeff Charlton has trained, gained certification and worked across the United Kingdom and United States for approximately 25 years. See JeffCharlton.ai for his technical background and experience ↗
9. One evidence-led completion question
Across jurisdictions, completion should mean more than painting, deodorising or making the surface look clean. Define the source-control goal, contamination-control goal, evidence to be collected, limitations and independent verification criteria before work starts.