Mycotoxins & endotoxins: harmful and silent air contaminants

In a tertiary or public building, air quality indicators are now closely monitored: CO₂, VOCs, fine particles, temperature, humidity. These parameters are useful, but they are not enough to explain some very concrete irritants of daily life: persistent musty odor, “heavy” air despite good ventilation, occupants complaining of irritations, HVAC filters saturating too quickly.

In many cases, the problem comes from much less publicized biological agents: mycotoxins and endotoxins.

These toxins are not detected by conventional sensors and are not visible to the naked eye. 

Yet, they play a major role in the perception of indoor air and in the operational burden of the building.

Mycotoxins: toxins produced by molds found in damp areas

Mycotoxins are natural toxins produced by certain common indoor molds, notably Aspergillus, Penicillium and Stachybotrys.

They are not volatile, but they adhere to dust, allowing them to disperse in the building's air and be inhaled or deposited on surfaces.

In the tertiary and public buildings of Luxembourg, they are mainly found in :

• the wet technical rooms,
• the false ceilings affected by infiltration,
• the staff restrooms and showers,
• the archives,
• the poorly ventilated areas or prone to condensation.

The WHO reminds us that an excess of spores or mycotoxins in the indoor environment increases the risk of irritations, worsening asthma, and general symptoms such as fatigue, headaches, cough, or respiratory discomfort.

On the ground, this translates into recurring occupant complaints and problem areas that persist despite cleaning.

Endotoxins: fragments released by Gram negative

Endotoxins come from another group of organisms: the Gram negative bacteria.

These bacteria are naturally present in humid environments. They are not dangerous in themselves. The problem comes from their outer membrane, composed of LPS (lipopolysaccharides).

When these bacteria die or degrade — for example in a poorly maintained humidifier — these LPS fragments detach: these are the endotoxins.

These fragments attach very easily to :

→ dust,

→ textile fibers,

→ deposits in HVAC ducts.

Once associated with a dust particle, endotoxins circulate in the building and can cause a respiratory inflammation, a progressive decline in lung capacity and an exacerbation of diseases existing in sensitive individuals.

A simple comparison: dust mites

Just like the mite is not dangerous: it is its droppings and fragments that cause allergies,

→ it is not the Gram-negative bacteria themselves that are problematic, but their residues (the endotoxins).

Why can't we measure these toxins with sensors?

Today, no continuous sensor allows for the measurement of mycotoxins or endotoxins in a building.

The only reliable methods involve:

• air or dust samples,
• a laboratory analysis,
• heavy techniques (HPLC, LC-MS, LAL test).

This makes these measurements:

❌ expensive,

❌ one-time,

❌ difficult to use for daily monitoring.

In practice, a Facility Manager therefore relies on indirect indicators : humidity, condensation, dust, odors, filter saturation, occupant feedback.

What actions should be implemented on the operational side?

The essentials:

• maintain a controlled humidity (30–50 %),

• address the infiltrations and condensations immediately,

• clean the dust with HEPA vacuums,

• maintain the HVAC systems and humidifiers.

These actions limit future development, but do not destroy the toxins already present on surfaces and dust.

Biologically degrade the toxins: the micro-biodiversity approach of Indoor Forest

Some teams complement the classic approach with solutions based on positive micro-biodiversity.

The principle is:

→ introduce beneficial microorganisms capable of naturally degrading mycotoxins and endotoxins,

→ without water, without chemicals,

→ with continuous operation that stabilizes the environment in sensitive areas.

For operation, the expected benefits are concrete:

• less odors,
• less visible and microscopic dust,
• fewer occupant complaints,
• fewer remedial interventions in chronic damp areas.
• and a cost of 4€/m2/year which means an unbeatable ROI of 5 to 7 weeks 

We can talk about it whenever you want >