My interest in ultraviolet (UV) light systems began a number of years ago with the introduction of a UV system in the discharge effluent stream of water at the wastewater plant where I work. If it works in water I thought, then why not air! The removal of pathogens from the water was most impressive and a mystery, So I hit the books and the Internet to learn more.
Here is a light summary of what I learned:
The sun generates ultraviolet rays. These rays are natures way of purifying the air. When sun passes thru a prism it’s broken into its component colors, thus giving the colors of the rainbow. Each color in turn has it’s own wavelength.
Ultraviolet light has three specific wavelengths that have particular applications:
UV-A is the source of suntanned skin, With its relatively longer wavelength, can penetrate the atmosphere. Applications include tanning beds and treatment of some skin diseases.
UV-B is in the middle wavelength of the ultraviolet spectrum and has principally been used to treat skin diseases.
UV- C or short-wave ultraviolet radiation, is used to destroy bacteria and other biologic containments in the air, in liquids and on surfaces. This is the area of my interest and study and use!
X-rays, BTW, are adjacent to UV-C on the spectrum. (They have even shorter wavelength).
It should be noted that the aforementioned are not all of the wavelengths available. Certain short-wave UV energies can be created by specially designed UV lamps, such as Ozone.
I learned that for many years the medical industry has been using UV light to sanitize rooms and equipment.
The Centers for Disease Control recommends UV lamps for their germicidal effect.
Through firsthand lab testing, I have seen the effect UVC has on pathogens (bacteria) in water. It renders them sterile.
So How Does it Work?
Using UV lamps provide a much more powerful and concentrated effect of UV energy than can be found naturally.
UV-C rays break through the outer membrane of microbes like yeast, mold, bacteria, viruses, algae. When the radiation reaches the DNA of the microbe it causes modifications. The DNA then transmits incorrect codes, rendering the microbe sterile and thus unable to reproduce.
Many industries utilize this type of process. Understand that I am not advocating that all microbes are being destroyed or sterilized in this unit! Only that through my use (Private and Professional) that I have seen a reduction in the overall colony count of microbial life forms. I use this system as just another line of defense in cleaner purer air. To put it into a simpler form, would you rather have to deal with hundreds of thousands of bacteria or hundreds?
My research found that UV light air purification systems were available and being used in schools, commercial buildings, federal buildings, many places.
Now that you have a light understanding ( pun intended ) of Ultraviolet Light you can see how I put this information to use to help better protect all my loved ones.
How I Used UV
The ability to protect yourself and loved ones from biological intrusion is a many-layered thing we all are preparing for: chemical suits, positive pressure safe rooms, filter masks, OTC medications and prescriptions to name a few.
Never being satisfied with the amount of space in my safe room (NBC-protected), I decided to see if I couldn’t incorporate a germicidal Ultraviolet Light System and positive pressure environment in my main living quarters to use as first line defense against poor air quality. I was off and running.
I knew since I constructed it, that my house was sealed exceptional well. Little did I know until I used a Slack tube manometer and did a static test with the air handler running and the house closed up tight. I had a negative pressure of .45″ water column vacuum. I concluded that I needed a fresh air return duct if I was going to use my air handler to try and pressurize the house.
My heating system uses a four speed motor (switchable) on the squirrel cage fan unit. All readings were taken with the fan set on a speed of med-high, resulting in a standard cubic feet per minute (scfm) rate of 1,170 cfm. My home has a combined cubic foot measurement of 4,940 cubic feet, thus resulting in the turnover rate of once every 4.2 minutes.
So, doing the math on the unit’s scfm capacity, and taking advantage of the variable speed motor I came up with a needed 60 to 75 sq. in fresh air duct to compensate for the tight construction [of my house] to bring my static pressure to 0. With full confidence in my math, I started. Next I needed filtration, HEPA filters of course. (I must state here that I’m working on a better filter arrangement than this but it’s sufficient for the time being). I installed one filter through the floor.
I then re-tested the static pressure. The static pressure in the house dropped to zero with one fresh air filter installed. The second took it to .2″ positive.
Here were my results:
- One filter = Equalized pressure
- Two filters =.2″ positive pressure
- Three = .45″ + positive pressure
Things looked pretty good at this point. I installed a third filter and the pressure went to .45″ positive with the in house air return in the full-open position. However, I still had a few concerns about air return temperature through the heat exchanger of the unit during the winter. But I pushed on.
I took a pressure reading from the slack tube at this point from the outside ambient pressure against the inside pressure with the air return in the full-closed position.
My pressure system looks pretty good @ .35” positive pressure running state.
Next, after researching the various light systems available I decided on the Calutec Blue UV, 72 watt, 2 bulb system. The system was designed for a 2,000 square foot house, but I have only 1,200 square feet. Bulb replacement cost is $18 ea. and the manufacturer says yearly replacement is advisable. Through personal hands-on experience, I’ve found that UV lamp life is reduced significantly after about 5,000 hours and I plan to replace them at that time on my system.
Having a raised platform on my heating system the return air duct was the perfect location for installation. The unit looked easy to install and would give me all the protection I felt could be attained with any such system. The return air and the fresh make up air would both be treated by the UV system before exiting the duct work with the fresh air being run through a HEPA filter. There are various locations for the unit and each has its merits depending on [the climate and] the configuration of the individual’s system.
I received the unit. I read the manual and then installed the unit. It was a very straightforward installation with minimal electrical work.
Safety Warnings
Here is a good point to tell you that UV-C light is nothing to play with:
NEVER expose eyes or skin to the UVC light from any source. Looking directly at UVC light can cause retina damage or even blindness. Only install unit in a closed area or duct system.
UV Lamps contain Mercury. As a kid, 50 something years ago mercury was cool to play with. It is a wonder that many of us are alive today. Use all necessary precautions if exposed to possible Mercury contamination from a broken bulb or any mercury for that matter.
So that was that, just another line of defense added to an expanding arsenal of personal protection apparatus.