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What Is An Electrostatic Precipitator?

There are many technologies in air purification.

Activated carbon, UV light, and HEPA or fiberglass filters are a few of the different strategies in particle removal.

One of the technologies you may have heard about is an electrostatic precipitator. This technology, which is effective for cleaning industrial fumes, has also been used for residential air.

However, when you learn more about electrostatic precipitators, you’ll discover that while they are effective for industry, they are not fit for your home. This is due to one specific risk: ozone.

But first, let’s learn about electrostatic precipitators, what they are, and how they work.

how electrostatic precipitator works

Electrostatic Precipitator Working Principles

At its most basic, an electrostatic precipitator is an air purification tool that uses electrostatic force to grab and hold dust and other particles.

It consists primarily of wires and collection plates, with a high voltage applied from an electrostatic field between the wires and the collecting plate, charging the air electrically and ionizing them in the process.

When airborne particles such as dust or pollen flows between the collecting plates, the particles become charged, which causes them to attach to the collecting plates. The air then flows through, leaving the particles behind. The result in cleaner, purified air.

The particles that have been collected are then shaken loose, scraped off, or washed away, and disposed of in a safe and environmentally-friendly manner.

static electricity

The principles at work in an electrostatic precipitator are essentially the same forces that hold balloons to the wall when you rub them on carpet or a shaggy sweater.

As you rub a balloon, electrons break free. The balloon then loses electrons and becomes positively charged, while the carpet, which gains electrons, becomes negatively charged.

With static charges, like magnetism, opposites attract, so when one item with a positive charge meets another item with a negative charge, they hold together.

Electrostatic precipitators work in essentially the same way no matter what the details.

As smoke and the gas stream is pumped out of a furnace or burner, it passes an initial wire or plate and gains the static charge. It is then collected by a second plate that has an opposite charge, where it is trapped.

There are, however, adjustments in the details that make the electrostatic precipitator work more effectively in different situations.

For example, there are precipitators that are scaled up to be more effective for low-sulfur coal, which produces more ash and therefore needs more energy to trap the high amounts of smoke.

One of the most common uses for electrostatic precipitation is in industrial applications, especially smoke.

Smoke may look like a gas, but it is fundamentally a mass of solid particles floating in the air. (Like a feather in the breeze.)

These particles can be charged, allowing them to be collected by massive, commercial-grade electrostatic precipitators.

According to the Thayer School of Engineering at Dartmouth, electrostatic precipitators remove over 99% of ash particles. In general, the larger the precipitator, the more effective they will be at removing particles from the air.

The Different Types of Precipitators

There are a few different types of precipitators that provide different levels of purification. Each type has its advantages and drawbacks.

Plate Precipitator

The most common and basic type of device is a plate precipitator. This device contains an initial row of vertical wires, which gives the particles a charge, while the following plates are used to collect and hold the particles.

This two-stage design (charging then collection) reduces ozone production, which can be harmful when inhaled. This creates a healthier air for people who may be working in the direct vicinity of the precipitator.

Wet Precipitator

Another common type of precipitator is called the wet precipitator, sometimes called a WESP (Wet ElectroStatic Precipitator.) These devices are commonly used to remove liquid droplets, especially sulfuric acid mist, from industrial steam.

This technology uses a tubular design that allows collected moisture and particulates to form a thick combination, or slurry. The design is very effective for content that holds a high amount of moisture or contains combustible particles. This system is like “dry” collection, but the collected particles are gathered using water sprays, irrigation, or condensation, which pulls the particles from the gas stream away from the collection plates or wires.

Commercial Break: “Flue Gas” Explained

When researching electrostatic precipitators for industrial and commercial purposes, you’ll come across a common term: flue gas.

A flue is a pipe or channel exiting a fireplace, oven, boiler, or furnace.

Flue gas, therefore, is the smoke leaving these stacks.

In most cases, “flue gas” refers to exhaust from power plants or industrial facilities, but the composition depends on what is being burned. It can be made up of nitrogen, carbon dioxide, water vapor, and particulate matter, as well as many other chemicals and pollutants.

History of Electrostatic Precipitators

Electrostatic precipitators date back to the early 20th century, when Dr. Frederick Cottrell, a chemistry professor at the University of California in Berkeley, applied for a patent on a device that charged particles and collected them using electrostatic attraction.

He applied for the patent in 1907 and the device was first used to collect sulfuric acid mist and lead oxide fumes, which were harming vineyards in northern California.

Ironically, Cottrell developed the device despite not fully understanding how it worked.

It wasn’t until research was conducted in Germany that the science behind electrostatic attraction was understood.

No matter; the device worked, and Cottrell was able to use profits from the machine to fund further research, experiments, and innovations.

Using an Electrostatic Precipitator at Home

When created for residential use, electrostatic precipitators are commonly called electronic air cleaners or simply “ESP’s” (for ElectroStatic Precipitator).

These air purifiers typically pull air first over an initial air filter, then pass the air over an electro-charging process.

After the particles in the air are charged, they pass over plates that collect the contaminants. Before the air is finally released, it passed through one more fine filter, resulting in clean air for the home or office.

At least in theory.

The Big Problem: Ozone

One major concern of these machines is the release of ozone and nitrogen oxides, which creates a health concern for many individuals.

While they often don’t produce as much ozone as an ozone generator, the chemical is a by-product of the air-charging process.

So, in effect it introduces pollution into your room.

We won’t get too deep into the molecular science behind the health risks, just know that electrostatic precipitators create a small runoff of ozone, which is harmful to skin, bronchial tubes, and lungs. Ozone is not meant to be breathed in.

Other Disadvantages of Electrostatic Precipitators for Home Use

Although less serious than ozone production, one of the main concerns with using electrostatic precipitators for the home is that they can be challenging and messy to clean.

This is because dust and smoke particles are collected directly inside the appliance and need to be manually removed. When cleaning, it’s easy to have dust, smoke, and soot become dislodged, creating a mess.

Or worse yet, the very particles you are trying to avoid can be breathed in.

Electrostatic precipitators for home use can collect dust, mold spores, and other large particles, but at much lower efficiencies than a HEPA filter. And as the plates become dirty, this efficiency drops further.

An ESP can trap organic compounds and pollen molecules, but it does not effectively capture smaller particles or gaseous chemicals.

Electrostatic Precipitators vs Ionizers It’s easy to confuse electrostatic precipitators with ionizers, but these two machines, while similar, are different.

They both charge the air, but while an electronic precipitator draws in air, charges it, pulls out the contaminants, and releases clean air, an ionizer simply releases charges into the surrounding room.

Ionizers charge particles however to not collect anything, so the particles simply stick to surfaces in your home. The particles may not be in the air, but they still reside in your living space.

Safe Alternatives to Electrostatic Precipitators

Although electrostatic precipitators can be effective for industrial flue gas, they can be harmful for home use because of the potential ozone production.

For this reason, none of the air purifiers from Oransi use electrostatic precipitation.

Instead, we use world-class HEPA filters, activated carbon, UV light, and other technologies to safely purify the air.

Electrostatic precipitators are used primarily to remove smoke and dust, so let’s look at a few safe alternatives...

OV200 Air Purifier

This is one of the most effective air purifiers for removing dust from the air, and the OV200 can also remove allergens, mold, pet dander, and even light odors. With a HEPA and activated carbon filtration system, this purifier removes 98% of all airborne allergens and particulates.

Max HEPA Air Purifier

The Max HEPA is one of the most cost-effective purifiers you can find for your home, and it can effectively remove dust, as well as bacteria, pollen, mold spores, and pet dander. It uses an activated carbon filter for light odors, giving you clean, healthy, refreshing air in any room.

Erik 650A Air Purifier

Strong enough for healthcare facilities and offices, the ERIK 650A is one of the most powerful air purifiers available. It removes over 99.99% of all particles, which means it goes above and beyond HEPA filters. Using a proprietary gas filter, this air cleaner is highly effective for removing smoke and odors.

Find Safe, Effective Air Purifiers with Oransi

You can have a top-quality air purification technology without the harmful risks of electrostatic precipitators.

Browse our large selection of air purifiers and you’ll find large and small home appliances that remove smoke, dust, and many other contaminants, giving you and your family healthy, refreshing air!
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