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Dirty Air in the Office – Fix it Now with Desktop Air Purifiers

I have written before on the health risks associated with unhealthy air in our homes and how to improve indoor air quality. However, many of us spend considerable time outside our homes in our offices at work. Our work place may not have adequate air quality. In particular, scientists tell us that office equipment such as printers, fax machines and computers generate Volatile Organic Compounds (VOC)s which may not be removed by the office air conditioning system.

Furthermore, since office machines are in close proximity to the people who use these machines, both at home and in offices, their effect on health requires urgent examination.

What the Scientists tell us

Laboratory tests have detected the following harmful emissions emanating from common office equipment:

Toluene, Styrene, Benzene,Chloroform and Metyl Chloride. In addition, the ozone emitted by printers can combine with other VOCs in the room and produce harmful secondary pollutants and ultrafine aerosol particles [1]. These tests also showed that emissions from laser printers were higher than those from ink-jet printers [2].

To address this air pollution created indoors it is recommended that cool and dry clean air be introduced close to the breathing zone of each individual [3].

To comply with this recommendation it is advisable that we keep on our desk a small air purifier that will protect our personal environment. This small air purifier, suitable for areas 50 to 150 square feet, does not have to be expensive. Many low cost small air purifiers are available in the market.

Desktop Air Purifiers

To select a suitable Desktop Air Purifier we must evaluate the quality of each of the main elements of the Air Purifier.

– Pre-Filter

– Main Filter

– Carbon Activated Filter

– UFC Light (optional)


Particulate matter (PM) air pollution is an air suspended mixture of solid and liquid particles of various sizes. Scientists classify the particles in 3 categories.

Coarse Particles – larger than 2.5 micrometer ( PM10) . Examples: dust, pollen, mold,spores,pet dander

Fine Particles – smaller than 2.5 micrometer ( PM2.5) . Examples: VOCs such as benzene, toluene and formaldehyde from smoking, cooking on gas stoves, cleaning fluids, solvents and pesticides.

Ultrafine Particles – smaller than 0.1 micrometer (included in the PM2.5 classification) Examples: vehicle exhaust gases, gases from atmospheric photochemical reactions, viruses.

The majority of the particles present in our homes or offices are large particles. These large particles can clog the main filter in the air purifier reducing its efficiency for capturing the smaller, more dangerous particles.

Therefore, it is very important that the air purifiers include a pre-filter to remove the large particles. The pre-filter should be easily removed so that it can be cleaned or replaced regularly. This will insure efficient operation of the Air Purifier.


There are mainly two types of filters for particle collection.

– Electrostatic Precipitation Filters (ESP)

ESP’s use a high voltage wire to charge incoming particles which are then collected on charged plates inside the air cleaner. These units are mostly installed in whole house ventilation systems. We will not examine this type of filters in this article, which is aimed only at Desktop Air Purifiers.

– Fibrous Media Filters

Within this category we recommend the High Efficienct Particulate Air (HEPA) Filters. These filters are manufactured as flat pleated sheets of different thicknesses. As the air is forced through the filter the particulates are attracted and get attached to the HEPA filter fibers. The HEPA filters offer the highest available particle removal efficiency of fibrous media filters. They usually have a removal efficiency of 99% or higher. There are two methods for evaluating fibrous media filters.

a ) Efficiency Testing

The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHREA) in their standard 52.2 specify a testing method. This method measures the removal efficiency of particles sizes 0.3 to 10 micrometers in diameter. The test results are reported as Minimum Efficiency Reporting Value (MERV) numbers ranging from MERV 1 to Merv 16. The rating numbers are based on the average removal efficiency for 3 particles sizes in ranges .3 to 1 micrometers, 1 to 3 micrometers, and 3 to 10 micrometers. The better the filter the higher the MERV number. The test method is very specific.

Filters with a MERV 13 rating must remove at least 50% of the 0.3 to 1 micrometer particles. This size of particles are the most harmful of human health. The HEPA filters are equivalent to MERV 16. Many filter manufacturers display the MERV number on their filter packaging.

b ) Clean Air Flow through the Filter

When the filters are installed in a portable Air Purifier the efficiency of the Air Purifier and Filter is measured in units of Clean Air Delivery Rate (CADR). This is a measure of the Air Purifier delivery of relatively clean air, expressed in cubic feet per minute (cfm).

In comparing different Desktop Air Purifiers we should compare their HEPA filter and their CADR ratings.


Carbon Activated Filters are an additional filter that is incorporated in the best Desktop Air Purifiers to adsorb odors from pets, smoking and cooking. In some Air Purifiers the carbon activated filter is combined with the pre-filter.


A UFC lamp is an ultraviolet germicidal lamp with a wavelength of 200 to 300 nanometers (nm) used to destroy germs and viruses. The UFC light has been shown to kill airborne germs including staph, influenza and pneumonia. One of the recommended Desktop Air Purifiers incorporates a photocatalyst TiO2 activated by the UFC light and combined with an activated carbon filter. This combination is reported to increase the pollutant removal efficiency and also to reduce the amount of secondary VOCs [4].

Although many scientists believe that UVC rays are not harmful to humans, there are others who differ from this opinion. It is possible to select a Desktop Air Purifier that includes an UFC lamp but the lamp can be turned off. So use of the UFC lamp can be optional. Or it could be used during business off hours when people are not present.

Comparison of 3 Excellent Desktop Air Purifiers





We must take the steps necessary to ensure that our environment is healthy. Clean indoor air is our individual responsibility, at home or in the office. I encourage you to look into Desktop Air Purifiers to improve your personal environment.

For details on the Air Purifier I recommend click here


[1] Hugo Destaillats et al. “Indoor pollutants emitted by office equipment”.A review of reported data and information needs. Lawrence Berkeley National Laboratory, Environmental Energy Technologies Division.January 2007,LBNL-62082

[2] S.C.Lee,Sanches Lam,Ho Kin Fai.” Characterization of VOCs,ozone,and PM10 emissions from office equipment in an environmental chamber”.Department of Civil and Structural Engineering, The Hong Kong Polytyechnic University,Hong Kong. Building and Environment 36(2001)837-842

[3] P.Ole Fanger. “Indoor Air Quality in the 21st. Century Search for Excellence”. Indoor Air/Volume 10, Issue 2,December 2001. Study from the Technical University of Denmark.

[4] C.H.Ao,S.C.Lee. ” Indoor air purification by photocatalyst TiO2 immobilized on an activated carbon filter installed in an air cleaner.” Department of Civil and Structural Engineering.The Hong Kong Polytechnic University.Chemical Engineering Science. 60(2005)103-109


Improving Indoor Air Quality – Getting Ready for Spring

Getting Ready for Spring

We all look forward to the warm weather, clear skies and spring flowers. We can once again open windows in the morning and late evening, letting fresh air in, thus providing adequate ventilation.

But spring also brings an increase in mold and allergens like pollen from outside air. Furthermore, we will be spending more time outdoors so we will be exposed to these allergens. It is important therefore, that the time we spend indoors is in a clean and healthy environment.

What Scientists tell us about Spring Health Risks

In addition to pollen and mold spores, springtime also brings less known dangers. A report by Daniel Jaffe, et al., published in the Geophysical Research Letters [1] shows that during spring there is an increase of background levels of ozone on the west coast of North America. This report shows that ozone in air arriving from the Eastern Pacific in the spring has increased by approximately 30% from the mid 1980s to the present

The elevated levels of ozone are a concern since when combined with small particles in the air, PM2.5, they affect the respiratory system. A Study of the Effects of Low-Level Ozone and Fine Particles on the Respiratory Symptoms in Children with Asthma by Janneane F. Gent et al.., published by the American Medical Association [2], concludes that simultaneous exposure to ozone and fine particles contribute to increase respiratory symptoms and the need for rescue medication use.

It is also known that Mold Allergy problems increase in the spring. Furthermore, studies show that risk of death from asthma during the pollen season is related to the level of Environmental Molds [3]. All the above risks suggest that we should remain vigilant and minimize indoor air pollution. Indoor Air Quality in our homes is our individual responsibility.

What should we do to insure Healthy Indoor Air in the Spring ?

We have discussed in other articles [4] that the science of clean air is still evolving. There is no scientific consensus on what constitutes “clean air “. Most of the standards are based on “perceived air quality”. Perceived Air Quality (PAQ) is the statistical average of the subjective assessments of air quality by those living in a home or working in a business environment.

Nevertheless, there are common sense actions we can take to improve our Indoor Air Quality (IAQ).

Eliminate Fine Particles (PM2.5) from indoor air

PM2.5 particles are those smaller than 2.5 micrometers. It is especially important to eliminate the ultra fine particles (smaller than .1 micrometers) since these ultra fine particles can translate from lungs to the blood system.Note: Definition of these particles and a discussion of the health risks posed by indoor air pollution can be found in Reference [5].

Do Not Smoke Indoors

Eliminate Volatile Organic Compounds (VOC’s)

These include fragrances, formaldehyde and other emissions from building materials and furniture. According to a Danish Building Standard the amount of VOC’s should be below levels that can be sensed by the occupants.

Monitor Carbon Dioxide (CO2)

Carbon Dioxide levels to be kept below 1000ppm. Must have Carbon Monoxide detectors since malfunctioning furnaces can be lethal.


Homes should be ventilated as a minimum at a rate of 7.5 cfm(cubic feet per minute) per person plus 3 cfm per 100 square feet of home size. Standards assume that number of home occupants will be equal to the number of bedrooms plus one. As an example a 2000 square feet home, with 2 bedrooms, would require a minimum of 82.5 cfm. [6]


Humidity should be approximately 35% RH in winter months and 50% RH in the summer.

Air Filters

Air Filters in the Air Conditioning System should be checked and replaced regularly. The Air Filters used should have a Minimum Efficiency Reporting Value (MERV) of 13. This quality filters remove at least 50% of the o.3- 1 micrometer particles.(These are the particle sizes that are most harmful to human health). The best filters, however, are the High Efficiency Particulate Air (HEPA) Filters. These filters are equivalent to a MERV 16 and remove 99% of particles. [7]

Air Purifiers

European Standards recommend that air should be supplied to the occupants cool and dry. In addition, the clean air should be introduced close to the breathing zone of each individual. Air Purifiers in the proximity of the occupants should be used. Or at least in the kitchen, living room and bedrooms where many of the indoor pollutants originate.[8]


Implementing the above recommendations will result in Clean and Healthy Indoor Air in all seasons.

Remember,Indoor Air Quality in our homes is our individual responsibility.



[1] Daniel Jaffe, et al.., Increasing background ozone during spring on the west coast of North America, Geophysical Research Letters / Volume 30, Issue 12

[2] Janneane F. Gent et al.., Association of Low-Level Ozone and Fine Particles With Respiratory Symptoms in Children with Asthma, American Medical Association, JAMA, October 8, 2003- Vol 290, No.14

[3] Paul V.Targonski, et al..,Effect of environmental molds on risk of death from asthma during the pollen season, The Journal of Allergy and Clinical Immunology, Volume 95, Issue 5,Pages 955-961






Improving Indoor Air Quality – Can Green Products Help?


We know that, since we spend 90% of our time indoors, reducing indoor air pollution is essential for a healthy environment in our homes. Some indoor air pollution comes as infiltration from outside, but we create a large percentage of the pollution through our daily activities. So the question is, can we minimize the pollution that we create by using “green products”. In this post we will examine this question and discuss our options.


Not much. Most scientific papers deal with specific contaminants and how they can be studied in a laboratory situation. Most papers are written by scientists for scientists or to get recognition by their peers. The individual papers do not shed light on the broad picture of healthy indoor environment. After reviewing tens of papers I could not find one with actionable information. Even if contaminants are identified the amount or concentration that should not be exceeded to avoid damage to our health is not defined. Furthermore, the cumulative effect of the presence of several contaminants is not studied.


However, some general reviews of literature on semi-volatile organic compounds (SVOCs) in the indoor environment present useful information [1]. The top five indoor exposure agents are combustion particles, bio aerosols, radon, carbon monoxide and volatile organic compounds (VOCs). In addition, there are also present semi-volatile organic compounds (SVOCs) that are emitted from consumer products that we find in our home environment. Unfortunately most of the studies show a lack of data on concentrations of chemicals in consumer products. So it is not possible to link their presence to health issues. These chemicals are present in carpets and textiles, furniture, building materials, flooring, cleaning products, health/personal care products and cosmetics.


Green products are products that have less impact on the environment or are less detrimental to human health than the equivalent traditional products. In general, they are energy efficient, free of toxic chemicals and require less earth resources to produce. Green products are also referred as sustainable and earth friendly. As they apply to indoor air quality the most important are the cleaning products, because it is easy to substitute green cleaning products for their toxic equivalent. Green cleaning products are desirable because they reduce our exposure to chemicals indoors. However, their use will not guarantee a healthy environment since they represent only a small percentage of the total VOCs emitted indoors. Therefore, we should use green cleaning products as much as possible, but they are not a substitute for Air Cleaners.


There is no scientific evidence that using “green” consumer products will improve indoor air quality and create a healthy indoor environment. Because new products are constantly introduced to our home environment, many of which include “additives” with unknown or undisclosed chemicals, it is very difficult to know if our environment is healthy.

Common sense dictates that we avoid using sprays and fragrances and that we provide adequate ventilation. Other than that, as insurance, it is a good idea to use Air Cleaners in rooms where indoor air pollution is created such as kitchen and bedrooms.


Indoor Air – Comfortable or Healthy?


The science correlating clean air with health issues is still evolving. There is no standard definition of “Clean Air”. As a result, most standards for building indoor air quality (IAQ) are established based on people’s perception of air quality. In this article we will examine both perceived air quality and actual clean air. We will present our conclusion and recommendations for achieving the healthiest indoor air possible.

Comfortable Air

Perceived Air Quality (PAQ), as the name indicates, is the subjective assessment of air quality by those living in a home or working in a business environment. Home builders want to build homes that meet the wishes of the occupants. To determine what standards must be achieved to that end the builders conduct field studies in which sample subjects are exposed to different environment conditions, and their satisfaction with that environment is recorded.

A typical study [1] varied three levels of air temperature and humidity and two levels of ventilation rate. The values for temperature and relative humidity were:

20 Degrees C/ 40% RH, 23 Degrees C/ 50% RH,26 Degrees C/ 60%RH

Ventilation in these tests was set as:

10 liters/ second per person

3.5 liters/ second per person

Other studies [2] have examined the effect of CO2 on air perception quality.


These studies show that there is not a single value for the parameters studied that would assure an acceptable perceived air quality. The studies only show that air is perceived as acceptable when it is cool and dry and unacceptable when it is warm and humid. The ideal conditions depend on your geographical location and time of the year. Ideal Humidity is between 30% RH and 50% RH. For example Canadian standards recommend 35% RH in winter and 50% RH in summer

Other recommended values are CO2 less than 1000 ppm and ventilation rate above 0.5 air change rate per hour( or 14 liters/sec per person).

Other factors are also considered for improving comfort. For example a Danish labeling system for building primary emissions of volatile organic compounds (VOC) [3] focuses on comfort by minimizing annoying odors and mucous membrane irritation. The values of the VOCs should be below levels that can be sensed by the occupants. These levels have nothing to do with health impact. As we can see the emphasis is on maximizing the air quality perception, not the health of the building occupant.

Healthy Air

The science of clean air is still evolving. There is no standard definition of “clean air”. Scientific studies have focused on specific issues related to the ambient air such as the effects of radon, formaldehyde, sick building syndrome, air particulates, VOCs and ventilation. But all these studies were focused on the specific problems noted above. There is no single science branch that addresses all the above factors together as one subject. However, there is mounting evidence of the importance of indoor air pollution and lack of adequate ventilation in establishing a healthy air environment.Getting an Air Quality Monitor for your home is a good first step to improve your indoor air quality. Continue reading “Indoor Air – Comfortable or Healthy?”


Winter Months Challenge

Winter is almost here and new challenges to clean indoor air are upon us now. In spring and summer we worry about outdoor allergens like pollen and also about pollution created indoors from cooking, and smoking, and VOC’s. Air conditioning keeps us comfortably cool in the noon and afternoon hours. Opening windows in the morning or late evening to let fresh air in insures that we have fresh outdoor air and meets the recommended ventilation rates. Air purifiers add another level of insurance.

But in the winter months’ ventilation is more difficult. We tend to seal the home tighter, add insulation to windows and doors to prevent heat losses and reduce heating costs. But these actions create new problems.

Lack of adequate ventilation allows pollutants to accumulate inside the house and operating furnaces add to the level of CO2 and even increase the risk of carbon monoxide poisoning.

We have to be more vigilant. Also, the holiday season with the added fragrances, to make the home smell “nice”, add to the problem with the increased emission of VOC’s.Click here to see my recommendation on a very efficient HVAC filter.

Importance of Ventilation

Ventilation is still necessary, we must expel the stale air and allow the intake of fresh air. Ideally we should have installed a heat recovery ventilator (HRV) that extracts heat from the stale air that is exhausted from the house and transfers it to the incoming fresh, but cold, air. It is a heat exchanger where the exhaust air warms up the incoming supply air. These systems may be expensive to install but will provide energy savings since the furnace will cycle on less frequently. However, even if you do not have an HRV in your home you still must have ventilation.

But I want to stress that you must have CO, carbon monoxide, detectors in your home since malfunctioning furnaces can be lethal. Continue reading “IMPROVING INDOOR AIR QUALITY – WINTER MONTHS CHALLENGE”

About me

Hello, I am Carlos Gusts, a retired Industrial Engineer.

Now that I am retired I have the time to research and study the subject that is my passion.

How to achieve healthy indoor environments

I have seen first hand how indoor pollution affects people worldwide.Calling attention to what

improvements are  possible in this area can make a difference in people’s lives.I want to help.

Reporting on current research,and evaluating new products,is the mission of this website.

If I can be of any assistance please feel to contact me.

All the best,

Carlos Gusts

P.S. As a retired person I am also involved in research related to what makes retired persons thrive,not just survive. If you are interested you can visit my website on the subject