Mould Testing in Portugal (ERMI)

Gathering mould samples for testing

Introduction

Mould testing in Portugal is a common issue in Portuguese homes, particularly in coastal areas like Cascais where humidity levels are higher. While visible mould is easy to identify, hidden contamination behind walls, under floors, or within cavities is far more difficult to detect.

Many homeowners and buyers ask:

“Should I test for mould — and if so, what type of test is best?”

Standard Mould Testing in Portugal

In Portugal, most laboratories offer the following:

• Air sampling – measures mould spores in the air at a specific moment

• Surface swabs – confirms mould on visible areas

• Material testing – analyses plaster, paint, or building materials

These methods can be useful, but they have limitations.

The main issue

They provide only a snapshot in time.

For example:

• Open windows can reduce airborne spores

• Weather conditions can affect results

• Testing one area does not reflect the whole property

What Is Dust Testing (ERMI)?

Dust testing, often referred to as ERMI (Environmental Relative Mouldiness Index), is a more advanced method developed to analyse mould contamination over time.

Instead of testing the air, a sample of household dust is collected from areas such as:

• Skirting boards

• Tops of doors

• Shelving

Wiping surfaces to gather dust for laboratory mould analysisThis dust is then analysed in a laboratory using DNA-based technology.

Why Dust Testing Is More Advanced

1. Detects Hidden Mould

Dust accumulates particles from all areas of a home, including:

• Behind drywall

• Inside wall cavities

• Beneath flooring

This means hidden mould problems are more likely to be detected.

2. Provides a Long-Term Picture

Unlike air testing, which reflects conditions at a single moment, dust testing shows what has been present over time.

3. Identifies Mould Types and Levels

ERMI testing can identify specific mould species and provide an indication of contamination levels, helping to assess potential risk.

4. More Reliable Results

Dust testing is less affected by:

• Ventilation

• Time of day

• Temporary environmental changes

Important Limitations

While dust testing is powerful, it is important to understand:

• It does not locate the source of mould

• It does not replace a physical inspection

• It should be used alongside professional assessment

How This Applies in Portugal

Currently, advanced dust testing such as ERMI is not widely available through Portuguese laboratories. For this reason, samples are typically sent to accredited international laboratories for analysis.

When Should You Consider Dust Testing?

Dust testing may be useful if:

• You suspect hidden mould

• A property has a musty smell with no visible cause

• You are buying a property and want additional certainty

• There is a history of moisture or damp issues

• Occupants experience unexplained health symptoms

A Better Approach: Combine Testing with Inspection

The most effective approach is to combine:

• Professional inspection (to identify the source of moisture)

• Thermal imaging and moisture testing

• Optional laboratory dust testing (to confirm contamination levels)

This ensures both the cause and the extent of the problem are properly understood.

Conclusion

Mould testing methods vary significantly in accuracy and usefulness. While standard air and surface tests can provide limited information, dust testing offers a broader and more reliable view of contamination within a property.

However, no test replaces a thorough inspection. Identifying and resolving the source of moisture remains the most critical step in addressing mould problems effectively.

“On Time. Every Time.”

Frequently Asked Questions About Mould Testing in Portugal

Is mould testing necessary in Portugal?Not always. In many cases, a professional inspection is enough to identify the source of moisture and visible mould. Testing becomes useful when contamination is suspected but not clearly visible.

What is ERMI testing and how accurate is it?ERMI (Environmental Relative Mouldiness Index) is a dust-based test that analyses mould contamination over time using DNA technology. It is considered more reliable than air sampling for detecting hidden mould.

Can mould be present without visible signs?Yes. Mould can develop behind walls, under flooring, or inside cavities where it cannot be seen. Hidden mould is often associated with musty smells or ongoing damp issues.

How much does mould inspection cost in Cascais?Costs vary depending on the size and condition of the property. A professional inspection typically provides far more value than testing alone, as it identifies both the cause and extent of the problem.

Should I do mould testing or just an inspection?In most situations, a detailed inspection is the best starting point. Testing can then be used if additional confirmation is needed, particularly in cases of suspected hidden contamination.