Photo-stoichiometer

What are hydroxyl radicals (OH·)?

The hydroxyl radical (OH·) is the most important oxidant in the atmosphere. It forms naturally when sunlight acts on ozone and water vapour, and in forests, when the terpenes released by plants meet small amounts of ozone. It is so reactive that it is known as the “detergent of the atmosphere”: it oxidises and breaks down pollutants, volatile organic compounds (VOCs) and microorganisms.

It is extremely short-lived, so it acts where it is formed and does not build up. This natural cleaning effect of outdoor air is called the Open Air Factor (OAF). That is why measuring oxidation in OH· radicals, and not only in ozone, better describes the real oxidising capacity of an environment.

What does the Photo-stoichiometer app do?

Schönbein reactive strips (potassium iodide paper) change colour in the presence of oxidants. The app turns that colour, a qualitative reading, into a quantitative one using the Monagas Variant: it converts the colour into the OH· radical emission rate.

Use it to check that devices such as Wellisair produce the right amount of OH· radicals, or to see how loaded with oxidants (bleach, chemicals) an environment is.

How the result is calculated

1. It reads the colour at the centre of the photo and normalises it so it does not depend on the lighting.
2. It compares it with 18 reference patterns of four oxidants (H₂O₂, HClO₂, Cl₂ and O₃) and shows the three closest with their concentration.
3. It calculates the OH· radical emission from the luminance (Y) of the normalised colour:

E_OH· = 1.502·10¹⁶ · e^−0.1964·Y   molec·cm⁻³·s⁻¹

Oxidation levels and Open Air Factor

The app only asks for camera access. The photo is deleted right after its colour is read, and nothing is stored or sent.

What is Wellisair and what does it do?

Wellisair is an air disinfection purifier that works differently from conventional filter-based purifiers. It recreates what happens in forests: it makes the terpene oil in its cartridge react with a small amount of ozone to generate hydroxyl radicals (OH·) and spread them indoors.

• According to Wellisair, it continuously generates about 8,000,000 OH radicals per cc (normal air contains 200,000–8,000,000 per cc).
• OH radicals take hydrogen (H) from the proteins on the surface of bacteria and viruses, inactivating them, and become water (H₂O) that returns to the air.
• They also remove harmful gases such as VOCs through a series of reactions.
• It uses no filters. The technology began as a military defence technology in Europe and has been used in European hospitals since the 1990s.

Wellisair also offers more products with this technology: WADU-BIZ, CLENUVO, industrial modules and cartridges.