Reactive Defense is a term we coined to categorize various methods used to clean the air through ionization, photocatalytic oxidation, or electrolysis. Each method uses different technologies to generate a reaction with the air and its pollutants. There are various pros and cons to each method, and different studies have shown that they effectively reduce air pollutants.
Ionization for IAQ
Ionization works by charging water molecules (H2O) in the air with an electric charge. The charge causes the molecules to separate into hydrogen (H) and hydroxide (OH) as positively or negatively charged ions. When released into the air, the OH molecules can remove hydrogen molecules from viruses, mold, and bacteria which will eventually cause them to die. A whole-home ionizer is easy to install and is typically attached to the airflow system of your HVAC system and allows the reactive ions to flow through the ductwork and into your home. The ions typically last for 60 seconds and react with other molecules, meaning you need a lot of ions to treat a home effectively. Ionization does not remove particles from the air. When positively or negatively charged ions react with other molecules, they become heavier and attach to surfaces increasing the need to clean your home. Some forms of ionization produce ozone, a known lung irritant. While a good amount of research shows that ionization can effectively reduce harmful pollutants in the air, there is minimal research outlining the potential adverse effects of ionization.
Photocatalytic oxidation for IAQ
Photocatalytic oxidation (PCO) uses a light source, typically UV light, and a titanium dioxide catalyst to create hydroxyl radicals (OH). When released into the air, the OH molecules react with hydrogen molecules within an organism, such as mold, viruses, and bacteria, effectively killing them. This method was initially developed as space technology and is used in submarines to improve air quality. Depending on the product, a PCO device can be installed before the filter, after the coil, or packaged within an effective filtration system. There are some downsides to photocatalytic oxidation. First is that the UV light and catalyst need to be replaced, adding another item to your home maintenance checklist. When the hydroxyl radicals react with other molecules, they become heavier and attach to surfaces increasing the need to clean your home. Some forms of PCO produce ozone, a known lung irritant. While a good amount of research shows that PCO can effectively reduce harmful pollutants in the air, there is minimal research outlining the potential adverse effects of PCO.
Electrolysis for IAQ
Electrolysis breaks oxygen O2 into two separate atoms. The atoms combine with water molecules (H20) to create hydrogen peroxide (H202). The hydrogen peroxide can deactivate many microorganisms such as viruses, bacteria, and mold when released into the air. Electrolysis systems are typically installed in the ductwork of an HVAC system, and like ionization and PCO, the H202 deactivates and renders the particles harmless. Electrolysis systems are maintenance-free, and tests have shown long-lasting effects even after the system is off. Electrolysis does not remove the particles from the air but rather deactivates them and renders them harmless. Therefore the pollutants may settle onto surfaces, increasing the need to clean your home. Electrolysis also emits ozone, which is a known lung irritant. While a good amount of research shows that electrolysis can effectively reduce harmful pollutants in the air, there is minimal research outlining the potential adverse health effects.
The bottom line
Reactive Defense systems have been tested to reduce harmful levels of various pollutants such as VOCs, bacteria, mold, and viruses. Ionization is maintenance-free; however, it may be less effective due to its operation. Because it separates H2O, they can simply reattach, making it very difficult to release many ions in a large space. PCO requires some maintenance but may be more effective due to its operation. Because it uses a light source and a catalyst, it creates hydroxyls rather than separating water molecules. Electrolysis is maintenance-free and is quite effective in its operation. The oxygen molecule is split into two atoms and reacts with water (humidity) in the air; then, the H2O2 is effectively distributed in the home. While research has shown that each of these methods is effective, there is not enough study outlining some of the adverse health effects that may arise from each of these methods. For example, some solutions produce a small amount of ozone, a known lung irritant, and there may be other by-products associated with these methods. A properly designed HVAC system with good filtration, proper ventilation, UV purification, humidity control, system cleanings, and good source control practices will reduce the need for reactive defense systems. Nonetheless, reactive defense systems may be a good choice to supplement your existing system and is a more cost-effective approach to indoor air quality control.