"Air, Water and Surface Purification Experts Since 1951"

INDOOR AIR PART 1

  The Age of Man - Problem Discoverer - began as soon as he first started to proliferate across the face of planet earth.  A profusion of other life forms were encountered, all competing for more or less the same basic fundamentals of existence - something to eat, something to wear for protection from the elements, and somewhere to hide safely while resting from the day's labors.

    As he grew in numbers and expanded into new territories, man used his ability to reason and found answers to these problems, thus progressing into the Age of Man - Problem Solver.

     Concurrent with man's ever increasingly complicated existence was his sophisticated appraisal of problems and their solutions - his curiosity propelled him into the Age of Man - Problem Evaluator.

    Now, grasped firmly by the talons of "The Scientific Approach", man has been carried into the dawning of another era - The Age of Man - Problem Confuser.  He has become a victim of his own data gathering, drowning in an ocean of information that he continues to generate.  Terminology grows increasingly more complicated and therefore progressively less understandable.

     Research scientists actively promulgate their published data in polysyllabic phraseology, so tortuous as to be almost undecipherable, so limited in scope as to be meaningless.

     The problem to be addressed in this paper is that of the deteriorating quality of air within structures, particularly those of private homes and smaller apartments and commercial office buildings.

     This deterioration in the overall quality of indoor is the result of several factors.

    When heating was done with open fireplaces, indoor air could not easily concentrate its contaminants because of the continuous and appreciable volume of air being drawn into the fireplace and up and out through the chimney - being replaced by an equal volume of outside (and presumably fresher) air.

     Most of us have fond memories of sitting in front of an open fireplace, watching the flames dance as they consumed the fire in a multicolored display of exothermal oxidation (translation:  the heat liberating reaction of the carbon in the fuel with the oxygen in the air).

     The heat from the fire was balanced by the coolness at the back of the neck, if memory is examined, due to the rush of  unheated air being drawn in by the fire.

     Switching from logs in an open fireplace in each room to recirculating indoor air through baffles warmed by the burning of methane or bottled gases did not eliminate this problem.  Each cubic foot of methane so consumed, requires about ten (10) cubic feet of air for complete combustion, this air is usually from within the building - in other words, some of the already heated air - which then has to be replaced by an equal volume of outside air.  This was one of the reasons why home builders followed traditional methods of construction that allowed for from 0.5 to 1.0 ACH (air changes per hour).

     Translated, this means an allowance for leakage indoors of a volume of outside air equal to from 50% to 100% of the total volume of air inside every single hour.  A private home 25 feet wide by 40 feet long all on one floor level, would have from 4,000 to 8,000 cubic feet of outside air getting inside every hour.

     This high a rate of air change would not be conducive to allowing appreciable concentrating of airborne contaminants indoors.  Attempting to seal off air leakage in this type of structure may actually cause significant problems, since the air required for combustion must come from somewhere.  If leakage in cannot meet combustion stochiometry, incomplete combustion will result, forming carbon monoxide instead of carbon dioxide.  In severe imbalance conditions, air flow will actually reverse, going down into the building from the chimney (instead of out from the chimney), bringing the carbon monoxide inside to mix with the indoor air.

     Many new homes and buildings now are equipped with gas fired furnaces having combustion air piped in directly from the outside.  The relatively small loss in efficiency in using colder outside air for combustion - about 1% for each 10^o F of cooler air temperature - is more than balanced off by not having to heat several thousand cubic feet of outside air up to indoor temperature every hour.

     In some areas, buildings have all electric heating (and cooling), requiring no indoor air transfer to the outside.  These structures can be very tightly insulated with triple panel windows and gasketed entry and exit doors.

     Reduction in the ACH value of a building saves on energy and fuel costs . . . but it results in an increase in the level of indoor air contaminants being recirculated.

     More carpeting means more entrapment of dust and dirt from footwear coming in from outside, constantly stirred up into the recirculating indoor air.  When floors were uncovered wood or ceramic, much of the dirt would have remained in place and have been picked up and removed by washing.

     Furniture coverings retain more settled airborne matter than did unadorned wood or metals; many plastic or plasticized surfaces actually attract dust, sent back into the recirculating air when dislodged by normal use.

     Odors generated by cooking use of tobacco products, the wearing of perfumes or colognes, scented cleaning agents also tend to concentrate as less inside air is exchanged with that from outside.

     Microorganisms can also accumulate.  Every time someone sneezes or coughs, an aerosol spray containing bacteria and/or viruses is released into the air; entrapped by dust or free floating in the air, microbes generated at any point indoors can be carried through the ductwork and dispersed back out into every room.  The so-called "sick building syndrome" is becoming a common occurrence in large structures; it is logical to assume that the same thing is happening in smaller buildings, such as private homes.   Involving few people, such a situation would hardly attract the attention of the news media, and might well go unnoticed by the very occupants affected.

     Central HVAC, complete with attendant ductwork, is the predominant feature of most structures erected in recent years - even those that are heated in whole or in part by solar energy, while they may not use ducts, nevertheless also have a common interior air with restricted exchange with the outside.

     Ducted air systems all have provisions for some type of filter.  That these filters do remove something is evidenced by the fact that they must be periodically replaced because they get dirty.  The fact remains, however, that the usual filter is so coarse that it can only trap the largest of airborne contaminants; odors, finer particulates and microbes all pass through unimpeded.

     To the average homeowner, a furnace filter is just another expense in a long list of expenses.  Cost is a more obvious feature than effectiveness.  With the profusion of newer types having finer texture and considerably better filtration ability, there has been a tendency to divert attention away from the greater cost per unit by overwhelming displays of scientific verbiage.

     Merchandisers would do well to note that, while this used to work in the old days, there is a growing, inherent distrust of overly complicated explanations in favor of a simpler, more understandable outline of a product's credentials.

     This same confusing situation exists in another area of air treatment - that of the growing use of ultraviolet energy to reduce the level of recirculating airborne microbes.  The microbicidal ability (i.e. the ability to kill microbes) of UV radiation in the area of 253.7 nm (a level far below the "visible range" of the human eye) was established a long time ago.  Repeated tests have demonstrated actual values required for destruction of specific microorganisms - based on the product of time and intensity.  High intensities for a short period of time or lower intensities for a long period are fundamentally equal in lethal action on bacteria.

     As far as is known, all types of microorganisms tested, including bacteria, viruses, and mold spores, can be destroyed by germicidal UV, although exact levels required may vary widely from one microbe to the next.

     Obviously, therefore, ultraviolet energy can be employed very beneficially in the ductwork of an HVAC system, to reduce the levels of micororganisms being carried in the recirculating air.  Certain basic rules apply.  UVC quartz lamps that emit principally at 253.7 nm are ideal for this purpose; the Slimline germicidal type, available in different lengths, is the one almost always used.   Retrofitting an HVAC system for UV is a straight- forward process, since complete units designed for this purpose are readily available.

     The typical unit consists of one (1) or more germicidal lamps connected to appropriate ballasts, all lamps and ballasts being mounted together on a single structure that is inserted through a hole cut into the sidewall of the HVAC ductwork.  NOTE:  Where this insertion is made depends upon the individual ductwork, the availability of adjacent electric power, and the relative ease with which the unit can be periodically examined.  When inserted, the unit faceplate will completely cover the hole so that all of the UV radiation is kept within the duct.  This is necessary since direct viewing of an operating UVC lamp by unshielded eyes can be damaging.

     The unit will have a shielded viewing port, suitable fusing, and a grounded power cord for connection into a standard electrical power supply of 60 Hertz, 115 VAC.  A unit that contains a meter to  measure the UVC lamp output intensity would be advantageous, since lamps require replacement eventually as the radiation gradually affects the quartz envelope even though the visible light from the lamp does not change.  It would seem obvious to maximize exposure of recirculating air in the duct to the UVC lamp(s) by placement perpendicular to the air flow; this way, the airborne microbes receive radiation before, at, and after the lamp(s).

     Furthermore, some type of internal duct face coating or covering that better reflects UV radiation than the duct face itself would also be beneficial, since the object is to maximize the lethal radiation of the microbial contaminants.

     So much for the basics.

    The tenor of the business world today is focused on finding a perceived need and then supplying an answer to that need.  As public interest swells, new companies are formed, each striving for some marketing ploy that merchandisers can use to promote their products over those of others.  There is an unwritten maxim that, unfortunately, applies more today than ever:  "If you can't impress them with facts, overwhelm them with the nitrogenous by-product of four footed life forms."

     Advertising - from commercials on television and radio, to newspaper and magazine advertisements, to sales brochures and bulletins - has become an empire of its own, flooding the public with a continuous deluge of product descriptions and claims.  A single company might spend billions of dollars annually, depending on the estimated size of the potential market.  Of course, the selling price of a product must include the costs of advertising that product.

     Chocolate candy bars used to cost a lot less when most of them were made by Hershey; Hershey was so well-known and had such little competition that they did not have to advertise at all.

     Striving for uniqueness, today's merchandisers often concentrate on product differences from others, even if these differences detract from the intended purpose of the product.  The further the deviation from basic facts, the more overwhelming the "pseudo-scientific" explanation for this deviation.  Quite often, this means that the advertising brochure is far more impressive than the product it describes.

     The UVC lamp(s), for example, could be inserted parallel to the air flow in the ductwork, even though this means that microbes can only be exposed to lethal UVC in that fraction of a second when they are carried directly over the lamp(s).

     The net effect would be reduction in the total lethal microbial radiation, whatever the claims to the contrary.  Lamps could be positioned on an interior duct surface, but this is also counterproductive, since almost 50% of the total UVC output could contact little or none of the air flow.

     In summation, therefore, a series of statements are outlined.  You are asked to judge each and decide whether it is fact or fiction.  Correct answers are given on the bottom of this page.

1.  The overall quality of indoor air today is as good as ever and represents no problem.

2.  Standard HVAC filters remove almost all of the airborne contaminants in the recirculating air.

3.  Contaminants released into the air in one room will carry throughout the entire interior of the building by means of the HVAC ductwork.

4.  Ultraviolet radiation can only kill some types of airborne microbes.

5.  The exact way that UVC lamps are positioned within the ductwork is immaterial, UV is UV.

6.  The effects of overexposure of a microorganism to germicidal UVC radiation are cumulative.

7.  It is very difficult to provide UV radiation in an existing HVAC system.

ANSWERS

1.  Fiction.  The quality continues to deteriorate as added insulation reduces the influx of outside air.

2.  Fiction.  Standard filters only remove the largest of airborne debris - everything else goes right through.

3.  Fact.  Sneezing in the kitchen will result in the spread of the causative virus into the air in the living room, bedrooms, etc.

4.  Fiction.  UVC radiation can kill any airborne microbe tested to date; the total amount of radiation required will vary from one microorganism to the next.

5.  Fiction.  The placement of UVC lamps is one of the critical factors in maximizing the germicidal effect on the recirculating air.

6.  Fact.  Effects on microbes by UVC are primarily a function of intensity and exposure time.

7.  Fiction.  Complete retrofit units are readily available, requiring only a cutting out of a specified hole in the HVAC ductwork to allow for unit insertion.  

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