OxyFile #539

Indoor Air Quality - A Different Approach

By H. Banks Edwards, P.E.

A review of current Indoor Air Quality (IAQ) literature indicate 
that a thorough inspection should be made of any internal source 
that could generate a pollutant and correcting the problem. The 
heating, air conditioning, ventilation and filtering systems 
should be reviewed for maintenance and compliance with current 
requirements and regulations. Special attention should be given to 
the problem of eliminating microorganisms that can cause mold, 
mildew, odors and disease that can be spread throughout the entire 
building area. Ozonation of the recirculated air should being 
suggested as a viable method of eliminating microorganisms 


For many years ozone has had a very limited application in 
buildings for the elimination of microorganisms. It has acceptance 
as a good odor eliminator in bars, restaurants, kitchens, homes, 
etc. The Occupational Safety and Health Administration (OSHA) has 
established 0.10 ppm (0.2 mg/m3) of ozone for indoor air and 0.12 
ppm (0.24 mg/m3) for ambient air.  Ozone made from air can be an 
irritant if the indoor ozone level is too high. 

The ozone level in occupied areas should not exceed 0.04 ppm/wt. 
The ambient ozone level world wide varies from 0.0l to l.00 
ppm/wt. with 0.05 being the average. In Houston, Texas when the 
ambient ozone level exceeds 0.I2, the number of days and hours 
that above this level are recorded. Between 1980 and l993, 1980 
had the greatest number of days and hours that the 0.1 level was 
exceeded. the figures are 58 days and 224 hours. July, August and 
September have the highest levels of ambient ozone. If pure ozone 
is as toxic as is claimed, much of our wild life would die as well 
as humans. 

Most of the ozone standards were developed before 1950 using ozone 
generators that were crude when compared to today equipment. The 
ozone used for their experiments was generated from air. Since the 
primary ingredients of air are oxygen and nitrogen, when ozone is 
generated from air, the products are ozone and nitrous oxides. 
Both nitrogen pentoxide and nitrous oxide are toxic to the 
respiratory system but pure ozone is not; therefore if the 
nitrogen products are removed from the ozone, the toxicity would 
be eliminated. Ozone made from pure oxygen will produce only ozone 
and oxygen. Ozone generated from air is called IMPURE OZONE, but 
ozone made from oxygen is called PURE OZONE.

If a person was working in a room filled with impure ozone (made 
from air, remember that the composition of dry air is 
approximately 78.0% Nitrogen, 21% Oxygen and 1% other gases by 
volume) at the 1 ppm/wt level, his eyes nose and throat would 
become irritated after two hours. If that person was working in a 
room filtered with pure ozone (ozone made from oxygen) he/she 
could work and 8 hour day for a 5 day week without irritation. 

It is stated that the irritation level from impure ozone is about 
1 ppm/wt whereas the irritation level for pure ozone is about 40 
to 50 ppm/wt.

There are other types of impure ozone that are not usually 
mentioned but contain various types of irritants, they are:

1. - Ozone created by photochemical reactions with hydrocarbons
     (auto and truck exhaust). This type contains many different
     types of pollutants and is usually found in highly populated
2. - Ozone created by photocopiers.
3. - Ozone created by arc welding equipment.

4. - Ozone created by any high voltage equipment.


The application of IAQ to an old building requires a thorough 
inspection and evaluation of the air conditioning system and 
general conditions in the building. Due to the effort to decrease 
the energy costs of the air conditioning system, the ventilation 
requirements are reduced and the building made tighter. This 
should create problems for IAQ in that the ventilation may have 
been reduced too much; therefore, steps must be taken to correct 
this problem. Other types of complaints that are found in old 
buildings are; improper ventilation in that the air is either 
drafty or insufficient in various locations; odors due to 
perfumes, smoking cooking, labs and blue print rooms, rest rooms, 
etc, contamination from building materials, odors from outside, 
poor temperature and humidity control and improper or poor 

Tables 1 and 2 present an interesting review of the concentration 
of pollutants that are lower indoors and the concentration of 
pollutants that are higher outdoors. 

The equipment evaluation will include an inspection of the 
ductwork system for leaks and having them cleaned to eliminate any 
breeding places of microorganisms, having the fans and housing 
cleaned (blower chamber in large systems; special attention should 
be taken relative to the make-up-air. If the intake is below the 
second floor level, it is suggested that a separate filter be 
installed to reduce the particulate load on the air conditioning 
system filters. A review of the control system is necessary to 
determine if it is operating properly and does it comply with the 
needs of the building . After making a thorough review and 
evaluation of the heating and cooling equipment, consideration 
should be given as to whether this equipment meets the needs of 
the present requirements . 


The quality of the indoor air refers to the levels of allergens, 
odor and microorganisms. The air conditioning system filters 
should be designed to take care of the allergen problem. It should 
be remembered that A FILTER IS A CAFETERIA FOR BACTERIA and a 
special method of cleaning, the filters must be used that will 
eliminate the microorganisms.
The odor problem can be handled by using activated carbon filters 
in the air conditioning filter bank. These filters are rather 
expensive and require a greater amount of labor than the standard 
type of filter. They will collect microorganisms; therefore, it 
might be difficult to disposing of the filters. Since ozone is an 
excellent deodorant, it can, also, destroy microorganisms.
There are many methods of eliminating microorganisms but only a 
very few are safe to use in human occupied spaces. Four that can 
be used in occupied space are covered in the next section. 


1 - VAPORIZED TRIETHYIENE GLYCOL. At one time this method was 
approved by the Veterans Administration for use in their operating 
rooms. One of the objections is that it will only kill organisms 
that are air borne and not on surfaces. Also, if the adjustments 
of the triethylene glycol are improper, it can dissolve paint, 
thus causing trouble. The unit is a liquid vaporizer complete with 
glycol tank, heating element, fan and sensitive controls. The 
glycol is rather expensive and the tank needs regular attention. 
The vaporizer takes air from the ductwork, passes it through the 
vapor zone and returns the treated air to the ductwork. This does 
not remove odors. 

2 - ULTRAVIOLET GERMICIDAL LAMPS. This is a very effective method 
of eliminating organisms. The bulbs are installed in the ductwork 
at right angle to the air stream and are mounted in a frame that 
can be removed easily. The UV system consists of UV bulbs, 
transformers, on-off switches rheostat to control voltage, pilot 
lights and a elapse time meter to meter the running time of the 
bulbs. 12 inches each side of the bulbs on the interior of the 
ductwork bright and shinny aluminum should be installed. The bulbs 
must be wiped clean monthly, at least, for good results. The life 
of the bulbs is generally one year or less.  The organisms must 
pass through the UV light to be killed. UV does not have a 
residual time therefore there is no secondary effect.. UV light 
will not remove odor. 

3 - OZONATION SYSTEM. The ozone system consists of an ozone 
generator, and oxygen generator, operating and safety controls, 
running hour meter and an ozone monitor to control the ozone 
level. The ozone generator will deliver PURE OZONE (without oxides 
of nitrogen) to the ductwork air. This ozone will eliminate odors 
and reduce the microorganism level. The ozone system should be 
checked by a service man regularly to be certain that everything 
is operating as it should. 

Since the ductwork system, especially old building, could have 
pockets of microorganisms, mold, mildew etc., it is recommended 
the it should be purified prior to being put into operation. This 
purification would consist of operating the ductwork system using 
ozone at a substantial level above the standard operating level to 
destroy the accumulated organisms. This level should be between 1 
and 3 ppm/wt (substantially above the usual 0.0250 ozone level in 
the occupied areas. The ozone in the occupied area should not 
exceed 0.040 ppm/wt but the operating level should be about 0.0250 

4 - COMBINATION OF UV AND OZONE. This system Can be designed so 
that it will have the advantages of both the UV and Ozone systems. 
The UV lamps will have pure quartz glass rather than synthetic 


Clark E. Thorp states that Webster defines the word toxicity as 
the degree of "poisonousness". To state the toxicity of a 
substance however does not necessarily imply that the substance is 
poison. All substances are toxic to the human body if taken in 
excess of the normal human tolerance.. Chlorine is used to make 
mustard gas - a poison gas, yet we drink chlorinated water. 
Doctors use a medication to thin the blood of patients with high 
blood pressure, yet this same substance is a deadly rat poison. 
Water is essential to life but we can drown in water. When 
specifying the toxicity of a substance, we must give the maximum 
allowable dosage per unit of time. 

The data included in the background section of this paper covers 
the differences between PURE and IMPURE OZONE: The toxic level for 
impure ozone is set as 0.10 ppm/wt. whereas, experience indicates 
that the limit for pure ozone could be as high as 40 to 50 ppm/wt.  
Since all of the limits on the use of ozone have been based upon 
the use of impure ozone a new set of standards should be developed 
for pure ozone. At the same time reference should be made 
regarding the interference of nitrogen oxides upon the performance 
of ozone. 


One on the primary aims of IAQ is to reduce the use of energy in 
the air conditioning system and eliminate pollution. ozone can 
make major contributions in this regard, such as 

1 - Treating the cooling tower with ozone instead of multi-
   a - The cost of chemicals is eliminated.
   b - The condenser tubing bundle will stay clean; thereby 
       reducing the compressor head pressure, and saving as much 
       as 10% of the power consumption and increasing the 
       compressor capacity by about 6%. 
   c - Since the blow-down rate can be reduced buy up to 100%, 
       major savings will be made in water usage; thus, reducing 
       the cost of water and waste water treatment.  In areas 
       that have serious water restrictions, this is important.  
   d - The potential problem of Legionnaires disease is 

2 - By injecting ozone into the conditioned air in the ductwork, 
odor will be eliminated and the air will be much fresher; thereby 
making it possible to reduce the amount of make-up air needed. 
This will reduce the operating cost..

3 - Hospitals and other types of buildings located in a medical 
environment should  realize that one buildings exhaust air is 
another buildings fresh air.   Because of this, serious 
consideration must be given to the quality of the make-up air. A 
practical answer would be to ozonate the make up air. 


1 - By ozonating the conditioned air the odors in the building 
should be eliminated and the work environment will be pleasanter.

2 - By sanitizing the ductwork with ozone, the microorganism 
population should be materially reduced, thus reducing absenteeism 
due to sickness, etc. 

3 - Because the conditioned air is ozonated and the odor level 
reduced and the general freshness in the building improved, the 
quantity of make-up air required can be reduced; thus reducing the 
operating costs. 

Since ozone can make such a major contribution to the Indoor Air 
Quality in a building it should be seriously considered as a 
component of any IAQ system. 



Sulfur oxide                         (Fuel combustion)

Ozone                                (Photochemical reaction with 

Pollen                               (Trees, weeds, grass)

Lead, Manganese                      (Automobiles)

Calcium, Chlorine, Silica, Cadmium   (Suspension of solids, 
                                      industrial emissions)

Organic substances                   (Petrochemical solvents, 
                                      natural sources, unburned 



Nitric oxide, Nitrogen dioxide  (Fuel burning)

Carbon monoxide                 (Fuel burning)

Carbon dioxide                  (Metabolic activity)

Spores                          (Fungi, molds)

Radon                           (Radon emissions)

Formaldehyde                    (Particle board, insulation, 
                                 furniture, tobacco smoke)

Perchloroethylene               (Dry cleaning)

Asbestos, Mineral & 
Synthetic fiber                 (Fire retardent materials, 
                                 insulation, furniture)

Organic substances              (Adhesives, solvents, paint, 
                                 pesticides, cosmetics)

Ammonia                         (Metabolic activity, cleaning 

Hydrocarbons, Acrolein Nicotine (Tobacco smoking)

Mercury                         (Fungicides, paint, thermometer, 

Microorganism                   (People, animals, plants)

Allergens                       (House dust mites, animal dander, 
                                 insect parts)