If you have researched indoor air quality or dry fog services, you may have come across a compound called peracetic acid. It is widely used for disinfection and sanitization across industries, but most homeowners have never heard of it. Here is a plain-language look at what it is, how it works, and why it shows up in conversations about mold and indoor air quality.

What peracetic acid is

Peracetic acid, sometimes written as peroxyacetic acid or PAA, is a liquid compound formed from acetic acid (the acid in vinegar) and hydrogen peroxide. On its own, it is a powerful oxidizer, meaning it breaks down the cellular structures of microorganisms such as mold spores, bacteria, and viruses.

It has been used for decades well beyond the mold world. The food and beverage industry uses it to sanitize equipment and surfaces. Breweries, wineries, and agricultural operations use it to keep their facilities clean. Healthcare settings use it as a disinfectant. One reason it is so widely adopted is that, when used correctly, it breaks down into water, oxygen, and a small amount of acetic acid, leaving no lasting chemical residue behind.

Why it is used to address mold and bacteria

Mold and bacteria are living organisms. To deal with them at the source, you need something that disrupts them at the cellular level rather than just wiping them off a surface. As an oxidizer, peracetic acid does exactly that. It is recognized by the U.S. Environmental Protection Agency as an antimicrobial active ingredient, and it appears on the EPA's Safer Choice list of ingredients evaluated for lower concern based on available data.

That combination of effectiveness and a favorable safety profile is why peracetic acid is the active ingredient in a number of professional disinfection and indoor air quality applications, including some dry fog systems.

How it is applied as a dry fog

In a dry fog application, an EPA-registered solution containing peracetic acid is aerosolized into extremely fine particles, smaller than five microns. Because these particles are so small, they behave more like a gas than a spray. They remain suspended in the air and follow the same pathways as airborne mold spores and bacteria, reaching surfaces and spaces that wiping or spraying cannot easily reach.

The "dry" in dry fog matters. Unlike a wet fog or a liquid spray, a properly applied dry fog does not saturate surfaces or leave moisture behind. That avoids introducing new dampness into a home, which is important because moisture is the very thing that allows mold to grow in the first place.

Using it safely

Like any oxidizer, peracetic acid must be handled properly. In professional applications, the solution is used at controlled concentrations, the space is ventilated appropriately afterward, and people and pets stay out of the area during the application and air-out period. Used properly, it is considered a safe and effective option. Used carelessly, like any cleaning chemical, it can be an irritant. This is one of the reasons these applications are typically handled by trained technicians rather than as a do-it-yourself project.

The bottom line

Peracetic acid is a well-established disinfectant used across many industries because it is effective against mold, bacteria, and other microorganisms and breaks down cleanly without leaving a lasting residue. When delivered as a dry fog, it can reach throughout an indoor environment without saturating surfaces. If you are exploring options for a mold or indoor air quality concern in your home, understanding the science behind the methods can help you ask better questions and make a more informed decision.

Frequently Asked Questions

What is peracetic acid?

Peracetic acid, also called peroxyacetic acid or PAA, is a liquid compound formed from acetic acid and hydrogen peroxide. It is a powerful oxidizer that breaks down the cell structures of microorganisms like mold spores, bacteria, and viruses, and is widely used to disinfect across the food, agricultural, and healthcare industries.

Is peracetic acid safe?

Peracetic acid is recognized by the EPA as an antimicrobial active ingredient and appears on the EPA's Safer Choice list. When used at controlled concentrations with proper ventilation, it is considered a safe and effective option, and it breaks down into water, oxygen, and a small amount of acetic acid without leaving lasting residue. Like any oxidizer, it must be handled correctly, which is why it is typically applied by trained technicians.

How is peracetic acid applied as a dry fog?

In a dry fog application, an EPA-registered solution containing peracetic acid is aerosolized into particles smaller than five microns. Because the particles are so small, they stay suspended in the air and travel the same pathways as airborne mold spores and bacteria, reaching surfaces and spaces that wiping or spraying cannot easily access. A properly applied dry fog does not saturate surfaces or leave moisture behind.

Have questions about your indoor air quality? Pure Maintenance of Texas serves Sugar Land, Fort Bend County, and Greater Houston. Call 281-220-1425 or schedule a free evaluation.