Electrostatic Filter and Ozone

[gsubrec]

I am considering getting a HRV, and this brand says it has a washable electrostatic filter
Do all electrostatic filters, by definition , generate ozone ?

[drk]

Electrostatic filters don't make any ozone.

[genesis]

Pulled this at Random off the internet.
koreaherald news



.................................................. .................................................. .................................................. ......


National






Air purifiers using negative ions have little effect


Air purifiers using negative ions have little air-cleansing effect and even emit high-level ozone that can cause respiratory illnesses, a government test has found.

By contrast, those with filters proved effective at improving indoor air quality and only discharged moderate levels of ozone, the government said after examining 45 products on sale.

The demand for air purifiers has recently surged following the recent yellow dust storms that blew across Korea from China and the "well-being" trend.

Negative ion air purifiers account for around 20 percent of air cleaner sales with another 52 percent of the market taken by filter purifiers, said the Ministry of Environment.

Negative ion air purifiers were known to create negative ions found in mountainous areas and near waterfalls where the air is pure and healthy.

However, those on sale have only a minimal ability of collecting dust and removing harmful substances, the ministry said.

They also generate ozone up to 10 times more than the permissible level, the government said.

Nearly 70 percent of those gave off up to 0.580 ppm (parts per million) ozone, a figure far higher than the permissible level of 0.05 ppm.

"We are concerned about possible damage to consumers," the ministry said in its news release.

It refuted claims by some groups that low levels of ozone can act as a powerful purification element.

"Research has found that ozone has little effect on getting rid of air pollutants indoors," it said.

Therefore, it advised customers not to purchase products that advertise the effects of removing pollutants and odor through generating ozone.

The ministry said it will further inspect all air purifiers.

(hjjin@heraldm.com)


By Jin Hyun-joo




2006.05.10







¨Ï Copyright 2002~2004 Digital Korea Herald. All rights reserved

[gsubrec]

If electrostatic filters dont cause ozone, then what filter causes ozone ?

[drk]

Electronic, UV

[gsubrec]

What exactly is the difference in operation between a electrostatic and electronic filter and how does this mean that the electrostatic filter does not cause ozone pollution, whereas the electronic filter creates ozone

[genesis]

Active Electronic Filters (electrically charged filters). These filters are composed of
a loosely woven mat of fibers that can hold an electric charge. When they are actively
charged, they attract airborne particles to them. This dramatically increases their
capture efficiency. They have 95% efficiency at capturing particles as small as 0.3
microns in diameter. The filters are inexpensive. But, the initial cost for the filter
housing is significant. These filters are only mildly effective at removing odors. They
remove mold spores and bacteria from the air. They do not remove viruses from the
air.

Electric Field Devices. These devices place a strong and sometimes oscillating
electric field upstream of the air filters in an air handler. They claim to cause particles
that move through the field to be displaced and to collide with each other. This causes
small particles to stick to big particles and make them even bigger. An air filter
captures the bigger particles. These systems do not work because the particles do not
remain in the electric field long enough to collide with one another. Furthermore, the
high voltage that is required to maintain the electric field can be dangerous to service
personnel. These systems do not remove odors, mold spores, bacteria, or viruses from
the air.
Electrostatic Precipitators. These systems contain negatively charged wires
upstream of positively charged plates. Particles that pass near the wires acquire a
negative charge. Then, as they pass between the positively charged plates, the
particles are attracted to the plates. Airborne particles are very efficiently removed by
electrostatic precipitators, until the plates become dirty. The dirt on the plates insulates
them. This renders the system ineffective. In a home environment, this process takes
about 7-days. In a commercial setting the insulating process is even faster. Therefore,
the plates need to be cleaned at least once per week to remain effective. Cleaning is
seldom done this often, leaving the system totally ineffective most of the time.
High Efficiency (HEPA, ULPA) Filters. These filters are very efficient at removing
both small and large particles from the air. HEPA and ULPA filters efficiently remove
mold spores and bacteria from the air. They do not capture viruses. They are very
resistant to airflow across them and are quite expensive. HEPA and ULPA filters are
the current standard for removing small particles from the air. They do not remove
odors from the air.
Ionizers. Ionizers contain a thin cylindrical metal rod with a pointed tip. They
produce tens of thousands of negative ions that jump off the pointed tip and into the air.
These negative ions become attached to the particles passing nearby. The negatively
charged particles are attracted to nearby surfaces. These surfaces include the air
filters, the inside of the air handler, the inside of the air ducts, the walls in a room, the
floor in a room, the ceiling in a room, and the plenum above the ceiling. Within a short
period of time, the air handler, the ducts, the occupied spaces, and the plenum become
coated with dust. The dust particles are removed from the air. But, they are captured
in undesirable locations, creating a maintenance problem, a fire hazard, and aesthetic
issues.
Ozone (activated oxygen) Generators. Ozone generators produce the gas Ozone
and release it into the air. Ozone is an oxidizing agent. When an Ozone molecule
contacts an odor molecule it chemically reacts with it, producing a new compound.
Repeated oxidation events like this eventually produce Carbon Dioxide and water
vapor. Ozone is only effective as an odor-removing agent when it is at concentrations
greater than about 300 parts-per-billion in the air. Inside occupied spaces it is
regulated to stay below 30 parts-per-billion. Therefore, Ozone is not an effective odor removing
agent in occupied spaces. Ozone is effective at removing odors in
unoccupied spaces where high concentrations can be maintained. Ozone does not
remove particles from the air or destroy biologically active particles in occupied spaces.
Passive Electronic Filters (washable filters). Passive electronic filters develop a
static charge on the filter media as air passes through it. This charge attracts particles
to the media and they cling to it. As the fibers of filter media become insulated with
particles, the electric effect diminishes and stops. Therefore, these filters require
frequent washing. They can remove large particles from the air. But, they aren’t
efficient at removing small particles. These filters do not remove odors, mold, bacteria,
or viruses from the air.

[drk]

In layman terms! The electronic is charged by 110v this power is sent through the cells in the air stream. as the dirt passes by the sells it sticks to the sells. Electrostatic uses no electricity. It is a plastic filter and when the air passes through the filter is causes static electricity and the dirt will stick to the filter.

[cem-bsee]

the $500 (+ install) electrostatic whole house filters have a grid of high voltage charged wires -- like those used in power plants (precipitrons)

worked good for my Mom in early 1960s --
I cleaned her Honeywell unit at u-squirt-em car wash ~6 week intervals.

[pstu]

>>the $500 (+ install) electrostatic whole house filters have a grid of high voltage
>>charged wires -- like those used in power plants (precipitrons)
>>worked good for my Mom in early 1960s


That brings back memories. My parents had something that sounds like that, also from a house in the 1960s. Dad had hay fever and we really believed it helped. Sometimes would make a bug-zapper noise. Also remember the filter cleaning to be a chore, but perhaps it would be worthwhile for some people.

Naive question -- does this correspond to any products made and sold today? If so could you drop a couple names?

Thanks very much -- Pstu

[wptski]

I have a Honeywell F50A EAC on a Lennox HVAC installed in the early eighties, I think! Last summer after cleaning the elements, I discover that it wasn't working. The power supply was bad, obsolete and replaced with a updated supply. I read that it's supposed to stop particles down to .5 micron. After several hours the count is down around 100. Outside count was 12768.

I have a laser particle counter. Yesterday and this has repeated itself many times. Total particle count on a quick six second test was 2200. After one hour of running the fan on manual(EAC), no AC, is was 325. It is reducing even the .1 microns as well but not as much as larger particles.

I don't know if the updated power supply has increased its performance or what??

[Docfrugal]

[QUOTE=genesis;1100758]Active Electronic Filters (electrically charged filters). These filters are composed of
a loosely woven mat of fibers that can hold an electric charge. When they are actively
charged, they attract airborne particles to them. This dramatically increases their
capture efficiency. They have 95% efficiency at capturing particles as small as 0.3
microns in diameter. The filters are inexpensive. But, the initial cost for the filter
housing is significant. These filters are only mildly effective at removing odors. They
remove mold spores and bacteria from the air. They do not remove viruses from the
air.

What is the effect of ozone on such electrostatic filters? Will it decrease the efficacy of electrostatic filters on air cleaners or respirators? We used to have AprilAire which uses both HEPA filters, a prefilter and UV. We were told that UV killed pathogens and generates ozone to clean the smell. Currently, we have a Honeywell honeycomb, an electrically charged plate, and a prefilter. No HEPA. The air does not smell as fresh. Can you recommend your preference of either or of a different system? Or should I just replaced the honeycomb? We were told it was good for 10 years. This is the 8 th.what can I do to remove cooking odors in addition to opening doors and windows. Thank you.
Thank you.

[jmt834]

Most materials I've seen about electrostatic filters say they do produce ozone as a by-product. Many health organizations warn about it. For example, the sate of CA published, "Air cleaners that utilize ionizers and electrostatic precipitators are other types of devices that emit ozone, but do so as a by-product of their design and function. These devices are designed to electrically charge particles in the air and cause them to attach to surfaces in the room, such as walls or floors. Ozone is released through the charging process, although these devices typically emit much less ozone than ozone generators." (Hazardous Ozone-Generating Air Purifiers, on ca_gov). I would post a link but apparently. Im not allowed. I'm sure s simple Google search would turn up multiple similar sources though.

[IndoorAirNerd]

Electret - a filter that has fibers with an electrostatic charge. This filter is not plugged in and doesn't produce ozone. Similar to an N95 mask.

Ionizer / Electronic air cleaner / Electrostatic precipitator - these can either purposefully produce a lot of ozone, or incidentally produce a small amount of ozone. Those that say they don't produce ozone, probably still do produce some amount to varying degrees.

@gsubrec, you mentioned "washable", so my guess is that the unit has an electrostatic precipitator (positive ionizing wire and negatively charged collector plates that get cleaned).