Mould Risk Index

What is Mould Risk Index ?

  • Viliso Smart HHM Mould Risk Index is calculated based on the matrix using Temperature and Relative Humidity. Temperature and Relative Humidity are obtained from the sensors placed in smart HHM device.
  • Viliso smart HHM Mould risk index has taken reference of 6 levels Mould Index of VTT Technical Institute of Finland and mathematical model of mould growth by H Vitanen.
  •  Mould Risk Index helps you understand how your room air quality can be maintained at best level so as to reduce risk of the Mould. The Mould Risk Index helps you take suitable actions to improve the quality of air inside your room.

What is Mould ?

  • Mould is a fungus that grows in the form of multicellular filaments or spores called hyphae.
  • Mould causes biodegradation of natural materials, which can be unwanted when it becomes food spoilage or damage to property. They also play important roles in biotechnology and food science in the production of various foods, beverages, antibiotics, pharmaceuticals and enzymes.  Our topic here is to discuss the damage by mould to the human health and property.

How Mould grows ?

  • The most important factors influencing mould growth are moisture & temperature. Second important factor is availability of spores, type of substrate (surface or material) and exposure time.
  • During the initial phase, the spores of the mould settle on the surfaces and remain inactive until they can absorb moisture and nutrients from the substrate. If the substrate does not provide adequate nourishment and moisture, the spores do not germinate.
  • Once germinated growth generally occurs where the relative humidity (RH) is greater than 65% and the temperature is in the range 20 to 50°C. Most rapid growth occurs when RH is greater than 75% and temperature is between 25 to 35°C and the atmosphere is stagnant.

Health Effects associated with Mould

  • When the mould grows, touching or inhaling the spores of the mould can cause serious health effects.
  • The first immediate noticeable effect shall be musty odour. Subsequent effect can be headache, breathing difficulty, skin irritation, allergic reactions like aggrieved asthma.
  • WHO estimated that in year 2016 worldwide 339 million people reported to have asthma. According to WHO study about 81.7% Asthma patients report benefits of antifungal treatment which clearly indicates the reason of their asthma as exposure to some form of fungus.

Effects of Mould on Property

  • Mould spores are like seeds. When they get suitable environment for their growth they grow rapidly. As mentioned above most important factor for growth of the mould are suitable moisture and temperature conditions. Mould spores float in the air and rests on the surface of the object.
  • Under favorable conditions it starts to grow and starts damaging the material on which it is growing. It could be clothes, wooden material or damp ceilings or walls.

Critical relative humidity of different material as below

Materials Relative Humidity (%)
Wood and wooden products
Wallpaper and plastic coating
Mineral insulators (e.g. calcium silicate)
Thermal insulators (EPS, XPS)
Cement, Brick, Plaster

  • Critical relative humidity is a level where growth of the mould starts rapidly.
  • In order to control the growth of the Mould it is necessary to monitor air quality, particularly temperature and moisture.  Mould formation is possible only if growth conditions are met. Best method to control mould is to avoid Humidity. When Relative Humidity level reaches critical level Mould starts growing rapidly.  So, it is better to avoid excess humidity in the atmosphere and excess moistures in the objects. It is recommended that relative humidity be maintained below 60%, ideally between 30% to 60%, to prevent mould growth.

Important factors to prevent relative humidity are as below:

  • Use dehumidifier or air conditioner.
  • Eliminate the moisture source. Remove wet material from the room. If walls are having water seepage, repair it immediately.
  • Dry out the moisture damaged object/wall immediately.
  • Stop moisture increasing activity inside the room like drying the laundry.
  • Improve ventilation of room by opening the doors and windows.

Index Levels

1 & 2. Good

Air quality is good. Risk of Mould growth is low.

3. Moderate

Mould growth likely to start.

4. Poor

Mould is likely to grow on moist objects.

5. Very Poor

Mould will grow on vulnerable objects like wood and clothes.

6. Severe

High risk of mould on all kinds of objects in the room.

The Mould Risk index level might change frequently due to change in Temperature and Relative Humidity however actual growth and dyeing of the mould spore is slow and does not correspond with change in mould risk index. 

What Viliso Smart HHM device cannot do ?

  • Smart HHM device does not detect or destroy the mould spores in the air.
  • It cannot predict mould risk on objects having internal moisture.
  • A HHM device can only indicate risk of mould in the close area where it is placed.

Reference Documents

Copyright © 2021 Viliso Technologies Private Limited

Copyright © 2021
Viliso Technologies Private Limited