Siteseeing: US Nuclear Submarine Air Purification on your Desk January 16, 2004

Introduction

Page:: ( 1 / 6 )

As computer enthusiasts, we know how important good airflow is to stability and how detrimental dust can be. As dust builds up in your PC, it begins to insulate the case, increasing the system temperature. Your air intake and exhaust begin to clog up, reducing the efficiency of the axial fans used to prevent your CPU and videocard from melting. If you have airflow in your case and there's dust in the air, there's no escape. Even fast moving objects such as the blades of your CPU or exhaust fans are susceptible.

Slowly but surely, your PC begins to become more unstable and if you're unlucky, you'll experience the doomsday scenario of a dust-induced electrostatic discharge shorting your computer equipment.

To avoid dust, you can seal your case and consider liquid cooling techniques, but if you still want good airflow, there are only two good ways to keep a PC clean: vacuum regularly, or prevent dust from entering the PC in the first place. Since most of us are too lazy to vacuum, the better solution is to prevent dust from entering the PC in the first place. For this to be effective, the air purifier also has to be something low-maintenance – otherwise, you might as well vacuum.

I promised in that same article that FiringSquad would never review air purifiers. We will however look at one air purifier today, the Oreck Super Air 7. This air purifier is built with the same electrostatic precipitation technology used in the United States Navy's nuclear submarine fleet. Most importantly, in this instance, it's not marketing exaggeration. You see, Oreck famous (or infamous to some) for their lightweight but low-power vacuums does not make the Super Air 7 on its own. They're actually developed by Trion, who is the sole supplier of the air cleaners for US nuclear subs (and UK subs). The 5-stage electrostatic precipitation system is also identical to what's used in the submarines though clearly at a smaller scale. It's what I use at home.

[image]

Design

Page:: ( 2 / 6 )

When looking at how the Super Air 7 is built, it's interesting to see how all of the same principles that go into maintaining good system airflow apply. Let's take a quick look at the 5 stages of filtration before we go into greater detail.

[image]

Stage I: Pre-Filter

The pre-filter is a fairly large opener mesh that serves to trap large particles that may be in the air such as lint, hair, etc. It's essentially a grill to prevent large foreign objects from clogging the more critical components in the air filter.

[image]

Stage II: Positive Ionizer

The next stage positively charges the small particles that have made it through the pre-filter. These particles include things such as dust, smoke, and pollen.

Stage III: Collecting Plates

The bulk of the machine is in the collecting plates. These are negatively charged plates that attract the positively charged ions. Without a good collector plate, positively ionized particles can escape the air purifier and stick to other surfaces such as your wall. If you only had an ionizer without a sufficiently strong collector plate, you'd be throwing charged dust against the ceiling and wall.

[image]

Stage IV: Blower Fan/Charcoal Filter

Behind the collecting plate is a charcoal filter and large blower fan. Charcoal is used primarily for removing any odors from the air and is ideally replaced every 3 months. If you are not concerned about filtering odors and simply want dust prevention, you can run the system without a charcoal filter. The centrifugal blower fan, such as the ones used in the NVIDIA FX-Flow or Coolermaster Aero Blower Fans, is a very important design choice. Centrifugal blower fans direct air at 90 degrees from the intake and provide a solid column of laminar airflow as opposed to a regular axial fan (regular CPU fan) in which the center column is stagnant. This is a high-pressure system that ensures that air flows through all of the previous filtration stages and maintains better guaranteed airflow.

[image]

Stage V: Negative Ion Generator

Finally the Super Air 7 has a negative ion generator. This charges the clean air with a negative charge to "help freshen stale air." This ends up producing a bit of ozone although Trion insists that their filters do not produce any more ozone than a computer CRT. Note that this is not part of the core electrostatic precipitation technology, but is an additional feature.

Finally, the air passes through an optional fragrance cartridge about the size of a quarter which is basically similar to a concentrated "car air freshener." It lasts for one month.

5-Stage Cleaning

This is what the US Navy uses in their Trident subs, which were one of the most critical components of maintaining peace during the Cold War. Let's take a closer look at why this electrostatic precipitation technology ends up being very well designed by comparing it to the competition.

SIDEBAR: UK subs also use Trion air filtration.

Other filtration systems

Page:: ( 3 / 6 )

HEPA/ULPA Filtration

If the electrostatic precipitator technology has its claim to fame as being used in US nuclear submarines, HEPA filtration has its claim to fame as being designed in the highest level of Top Secret government projects. During the Manhattan Project, there was a need to filter very fine radioactive particulate contaminates.

The HEPA filter, or High Efficiency Particulate Air cleaner is a mechanical filter which is required to filter out 99.97% of contaminants 0.3 microns in size. ULPA (ultra low penetration air) filters catch more than 99.9995% of contaminants as fine as 0.15 microns. A mechanical filter is trivial to understand as it is simply a very fine grill that traps the physical compartments.

There are a number of reasons why this may be less than ideal. First, mechanical filters need very high air pressures to continually force air through the HEPA filter itself. Remember, cleaning 99.9999% of pollutants in the air is useless, if only a small volume of air is filtered. The actual HEPA filter itself has a very high resistance and so the fan needs more power than electrostatic precipitation systems, which have minimal air resistance.

As the HEPA filter clogs up, the filter rapidly becomes less and less efficient while simultaneously adding strain to the fan mechanisms. Finally, the filters are disposable and can be costly to replace.

It's important to keep your perspective. HEPA filters are great if you need absolute filtration – in terms of absolute performance, they're probably among the best. Austin Air HEPA filters have been used to protect US citizens living near chemical stockpile destruction facilities. However, chances are that you've got a working immune system and it's OK if there's some bacteria or viruses floating in the air. It's OK if the compounds that give your freshly laundered clothes a pleasant fragrance are in the air. It's dust that'll hurt your PC.

The main disadvantage of the system is the cost of replacement filters ($100 is not uncommon; some designs last 5 years, some only 1 year). In addition, HEPA filters tend to be bulky and noisy and are often overkill. Some HEPA filter manufacturers have taken on the razor model – they'll sell the unit at a bargain price, but then make huge profits on the replacement filters.

Ozone Generators

Page:: ( 4 / 6 )

Ozone Generators

You may have noticed that I said that the Super Air 7 does NOT release high amounts of ozone. This is a good thing. You may occasionally see low-cost products claiming to "freshen" the air by releasing ozone. They'll talk about ozone improving the body's immune system, or how ozone is the "fresh air" smell you have after a lighting storm. They may also tell you how great the ozone layer is at protecting the planet from UV rays.

All that said, ozone in your personal air is a bad thing. While there is some science that supports the hypothesis that ozone has local effects on the immune system, ozone is also a pulmonary irritant. OSHA has regulations against high levels of ozone in a work environment and even a personal ozone generator that fits in your shirt pocket will produce higher ozone levels than what is considered safe. In rats, ozone can affect cardiac rhythm and core body temperature, and ozone can make your pulmonary system more sensitive to irritants (a bad thing, especially if you have asthma).

Fanless Electrostatic Precipitation

The Sharper Image Ionic Breeze air purifiers have received notable fame for their silence. This silent design results in reduced airflow but thanks to its silence, it's easier to keep the air purifier running at night. A recent Consumer's Report article gave a poor rating to the Ionic Breeze systems because it did not move enough air to be effective. Sharper Image is suing them for product disparagement, unfair competition, and negligence.

Their statement is that although their air purifiers aren't effective when used short term, their products are designed to run 24/7 whereas other filters may be too noisy and only run for short periods of time. In the long run, they claim they're more effective. This may be true, but clearly in terms of air purification greater airflow is better as long as the collecting plates and positive ionizer have sufficient time to capture the dust.

Lastly, in use, Sharper Image Ionic Breeze can be troublesome to clean. In Los Angeles, some owners of the Ionic Breeze systems find that cleaning the plates was necessary every other day and that cleaning the plates was more arduous than vacuuming a PC, requiring repeated soft scrubbing. I'll talk about the Super Air 7's noise level and cleaning later.

SIDEBAR: Airflow is the key to everything. In cars, simply adding a K&N drop-in filter can improve the performance of your car.

Other Systems

Page:: ( 5 / 6 )

Negative Ion Generators

Some products claim to freshen the air by releasing negative ions exclusively, and in the case of the Super Air 7 a negative ion generator is added to the end. Any system that works primarily through negative ions is going to have a negative effect for your system.

First of all, isolated negative ion generators are going to be charging the dust in the air and depositing on your walls, on your PC, and all sorts of surfaces. You do not want to charge any particles without have a mechanism to collect and capture them. Second, there is also the question of having these components near your PC. In our hands-on tests, we have found no stability issues, although we have seen some manufacturer recommend keeping the ionizer 6-10 feet away from your PC.

There is however, some question of negative ions in the air and how it affects people. One of the earliest studies comes from a 1976 issue of Science, the hands-down most respected science journal. These researchers saw that positive ions routinely exercised a detrimental effect and that deprivation of small air ions increased the cumulative mortality rate of mice infected with the flu.. It's worth noting that PC monitors deplete negative ions in the air around it, so perhaps a negative ion generator in a PC room isn't such a bad thing. The jury is still out on this one.

In humans, there haven't been any convincing studies of any benefits. A study from the University of Washington showed no change in subjective or objective air quality with negative ion generators, and a Cochrane review showed no effect on ionizers (positive or negative) for people with asthma.

With the Super Air 7, ideally the air being negatively charged has had most of the dust filtered out. Nonetheless, the effects of negative ion release is up the air. Fortunately, the Oreck Super Air 7 has a switch in front to turn off the ionizer. This disables the negative ion release, but leaves the electrostatic precipitation components active. It's as if they were thinking ahead.

Carbon Filters

Carbon works superbly for absorbing odors although it does need to be fairly regularly replaced. The Super Air 7's carbon filters are fairly light. If odor is a bigger problem than dust in your room, you can find other filters such as those from Austin Air, which feature huge amounts of carbon. Alternatively, since the Oreck uses a high-pressure blower fan, it's also possible to make your own mod and add additional carbon filtering stages. Of course, taking care of the source of the smell is best.

Mitsubishi Plasma Pure

Mitsubishi has a product branded "Plasma Pure." This is a HEPA filtration unit with a UV lamp which is designed to provide Oxygen Singlet molecules, O1, Charged oxygen molecules, O2-, Hydroxyl Radicals, HO, and a low level of ozone, O3. The UV helps to sterilize the air passing through the unit, however two things to consider are that 1) you don't need to sterilize the air passing through the unit and 2) it's questionable if releasing oxygen singlets and radicals is a good thing.

Electrostatic precipitation

Electrostatic precipitation is popular for its lower cost, maintenance, and footprint. Oreck isn't the only manufacturer of consumer fan-based electrostatic precipitation technology. Products from companies such as Blue Air, and Friedrich are known to work very well and it's up to you to figure out how if how large of an area you would like to clean.

In-Use

Page:: ( 6 / 6 )

The Super Air 7 in use

Running at full fan speed, the Super Air 7 filters 8400 cubic feet of air/hour and traps up to 95% of airborne particles. Oreck also sells a higher-end Super Air 8 with a nicer finish. It also has a different pre-filter, which probably contains bactericidal compounds to allow it to kill the bacteria that the Super Air 7 does not. The Super Air 8 also has a silent mode which, like the silent PC case fans, seems to work simply by running at a slower RPM.

The Super Air 7 in maximum airflow mode is loud (not as loud as the GeForce 5800), however it is only the sound of moving air as opposed to a high pitch whine. It's not too bad. In the slowest mode, the Super Air 7 you can hear more of a whine when up close, but it's not bothersome at all.

The unit sells online for $199.99 or in a bundle at a retail store for $220 including a year’s supply for the cleaning spray for the plates and charcoal filters (with a $50 coupon, the in-store bundle can be $170, and if you buy two, it's buy one, get one half-off – see I told you Oreck was gimmicky).

Whereas cleaning the plates was troublesome with the Sharper Image Ionic Breeze, the spray can that was bundled with the air purifier works well. Simply spray the foaming cleaning solution onto the plates at an angle and allow it to soak and drip. After a few minutes, I run the collecting plates under water, and then let it dry. Oreck recommends cleaning the unit after the first week and then doing it once every month or two, or if the red cleaning light turns on.

Final Thoughts

I started this article by saying that a good air filter for PC enthusiasts needed to clean the air. When it comes to selecting an air purifier, you need to choose something that works at removing the pollutants you're interested in removing, and one that is appropriate for your room size and budget, taking into account the maintenance costs. The Oreck Super Air 7 seems to do that for me. It clearly works at collecting dust, is easy to maintain, and of course is built by Trion, who manufacturers the air filtration systems for the US nuclear submarine fleet.

Now pat yourself on the back because you've just witnessed history. You've just finished a home appliance review at FiringSquad.com. I can't imagine myself ever doing anything like this again in the future, but I'm sure many of you will admit that it was a fun one-time article to read. At the very least, you have to admit that only a truly hardcore gaming website such as FiringSquad would be crazy enough to do a serious tech article on a home appliance.



SIDEBAR: Surprised to see a review of an air purifier on FS? What do you think of the Oreck Super Air 7? Do you have any stories of your own to share? Speak up in the news comments!