PCO: Efficient Post-construction Remediation

Posted on December 12, 2017
by PureLiving

​Many clients have concerns about odors from construction and renovations and the impact on health of occupants in offices and homes. Much of the odor typically is caused by a chemical called formaldehyde, a known human carcinogen (1). While many countries have banned import and use of materials with high formaldehyde content, many building materials in Asia contain high levels of formaldehyde and other VOCs. While managing the construction process in advance is the best option (see our recent post to understand the different types of green building certification and how they relate to Indoor Environmental Quality), sometimes this is not possible. In these situations, one of the most effective ways to address concerns is treat the space with Photocatalytic Oxidation (PCO).

What is Photocatalytic Oxidization (PCO) Treatment?

Photocatalytic oxidization (PCO) is a type of remediation where a chemical, typically titanium dioxide, is vaporized and applied to furniture, walls, and floors in a room with high levels of odor or VOCs. Titanium dioxide is non-toxic and is commonly used in food additives. This substance weakens the carbon bonds in the VOCs, breaking up these bonds into smaller compounds over and over again until only safer substances like carbon dioxide and water are left behind. In our experience, PCO treatment is most appropriate when levels of TVOCs or other gases are more than twice the safe level and need to be immediately reduced. This generally occurs after construction or renovations, when new materials have been added to a space and not had time to off-gas.

PCO treatment

The treatment generally has an immediate effect of 40-90% reduction in VOC or odor levels. The remediation process leaves behind a clear antimicrobial layer which continues to inhibit gas release. The oxidization process works better with light (artificial or natural sunlight), but also works (though at approximately 30-50% effectiveness) in darkness.

Who should consider PCO treatment?

Anyone occupying a space which has undergone recent construction or renovation or is concerned about odors in their space.

What is Titanium dioxide?

Titanium dioxide (TiO2) is an anti-microbial metal created by a process which crystallizes titanic iron ore into a nano liquid form. When exposed to UV light, TiO2 becomes a photo catalyst oxidizer (PCO) as well, creating hydroxyl radicals and superoxide ions which are two times stronger than chlorine and 1.5 times stronger than ozone as disinfectants. TiO2 is safe and widely used in many household products such as toothpaste, food, and teeth whitening solutions. The advent of nano technology - making tiny particles out of metals that can penetrate most surfaces - has lead to several Japanese patents utilizing this nano TiO2 photocatalytic solution successfully in the Japanese marketplace due to its wide range of applications. For instance, the government uses this solution in some public bathrooms to keep them smelling fresh.

TiO2 coatings are applied to some highway guard rails to keep them looking new amid constant bombardment from hydrocarbons and VOC's from vehicle exhausts. TiO2 coatings are also widely used in the healthcare, food, janitorial, auto, and construction business.

Many homeowners treat their mini-blinds, windows, furniture, bathrooms, showers, carpets, flooring and the like with similar TiO2 solutions to reap the benefits of VOC-free, clean, fresh indoor air, with maintenance-free surfaces. When microorganisms, smog, viruses, VOC, or any organic material comes in contact with the TiO2 treated surface, it also becomes oxidized. Even fabrics treated with this substance will not retain odors. Car interiors treated with Nano TiO2, even when submitted to second-hand smoke from several people for prolonged periods of time, will not retain any tobacco smell.

How does Titanium dioxide treatment work?

Pollutants in the air are repeatedly brought into contact with the coated surface by air movement and convection. As the organic pollutants, like germs and VOCs, strike the coated surface, they are decomposed by the TiO2. This decomposition occurs when the TiO2 breaks down the carbon bond keeping most organic compounds, like germs, together by facilitating the oxidation process through a photocatalytic reaction. This photocatalytic reaction breaks these carbon bonds, reducing the organic pollutants over and over again into smaller compounds until only carbon dioxide and water (safer substances) are left behind.

how does Tianium dioxide treatment work

What kind of airborne pollutants can be reduced by TiO2-coating?

The Titanium dioxide-coating decomposes nitrogen oxide (NOx), formaldehyde, benzene and other volatile organic compounds (VOC) in the air. These pollutants are decomposed to non-toxic compounds like carbon dioxide, water, and nitrates.

How does the odor elimination work?

Similar to the organic pollutants in the air, odorous substances in the air meet the coated surface through the airflow. There they are decomposed to odorless compounds like carbon dioxide (CO2) and water (H20).

How does the antibacterial effect of TiO2 work?

As bacteria meets the titanium dioxide coating, it decomposes the cell wall of the bacteria, killing the bacteria. If Nano-Titanium dioxide is used as a slurry, the bacteria gathers around the Nano-particles, and the titanium dioxide decomposes essential parts of the bacteria's interior, killing the bacteria.

​Is there scientific evidence for the efficiency?

The efficiency of titanium dioxide coatings have been analysed and documented by ample by scientific studies. On request, we can provide further information or links.

Is PCO harmful to people or pets?

Approved by the United States Food and Drug Administration (FDA), TiO2 is considered a safe substance which is harmless to humans and is used widely as a food additive and coloring.

Nano TiO2 liquid, a non-consumable form of the chemical, is made with a patented binding process that makes it possible for this liquid to penetrate and form a permanent bond with surfaces, meaning that after it dries to form a film on a substance, it becomes one with the surface. Nano TiO2 liquid should not be applied directly to pets or animals, but it can be used to keep pet bedding from retaining odors. Unlike fumigation, PCO-treated rooms can be occupied immediately after spraying.

How durable is the titanium dioxide film?

The durability depends heavily on the treatment of the coated surface and the surrounding conditions. The durability can vary between five and ten years, but the impact of the photocatalytic effect is unlimited.

Does a TiO2-coating change the hardness and the feel of the surface?

Titanium dioxide coating has a hardness of approximately 5H (pencil grade) after hardening. Coated fabrics and textiles do not change their feel after coating.

How long does the treatment take?

This depends on the size of the treated space and amount of furnishings. A typical 200m2 apartment can be treated in about 2-3 hrs as long as the rooms have been prepared in advance (this includes contents being removed from drawers and closets, and furniture moved away from walls). Offices typically are quicker to treat.

PCO treatment

How much does this cost?

Cost depends on size of the rooms to be treated. The typical cost is 30-45 RMB per square meter for smaller projects, which decreases as the space to be treated increases. There is a minimum project size of 2000RMB. Offices typically are less expensive to treat.

Does the coating work with sparse sunlight indoors?

The addition of silver ions in the coating greatly enhances the efficiency of the titanium dioxide coating under sparse sunlight. Silver ions have, amongst other things, an antibacterial effect that is enhanced in interaction with the antibacterial effect of the titanium dioxide. Silver doped titanium dioxide products are active even at low light intensities. This means the oxidization process works better with light, but it can also work in darkness, though at around 30-50% effectiveness.

How do I know this will work?

We recommend retesting one week after air treatment to verify that the remediation has been successful.

What if this doesn’t work? Are there performance guarantees?

PureLiving guarantees the effective of PCO treatment and has successfully used it in many projects across may types of spaces.

Testing before PCO treatment is essential to establish pre-treatment levels. If pre-treatment levels are less than twice the GB50325-2010 standard, then PureLiving guarantees that average post-treatment levels for TVOC, Benzene, and Formaldehyde will meet GB50325-2010 standards or treatment will be repeated at no cost until the post-treatment levels meet the standard. If pre-treatment levels are more than twice the standard, then we guarantee there will be a 50% reduction in pre-treatment levels following PCO treatment. If reductions in levels at least equal to this are not observed, then PureLiving will perform follow-up re-treatment at no cost to you until the standard is met.

Please note that all air testing costs, including pre-treatment and initial post-treatment, are the responsibility of the customer.

1 Source: Can formaldehyde cause cancer?  


About PureLiving

PureLiving is a leading indoor environmental consulting company with a simple mission: to help our clients create healthy homes and workplaces. Our expert team of building engineers, HVAC specialists, and environmental consultants advises clients on air and water quality, mold, asbestos and lead exposure issues and helps to improve their indoor environmental quality through testing to identify sources of pollution and then eliminating them. Our total range of solutions includes pollutant testing, design and installation of cutting-edge filtration systems, monitoring, and odor and chemical reduction.

With operations in six cities across China, Hong Kong, and India, PureLiving is the industry’s provider of choice for assessment, engineering, implementation, and monitoring of indoor environmental quality.