How to Measure and Remove Contaminants from the air


occupational hygiene

According to the WHO, around 92% of the air that we breathe is polluted. The condition is poorer in industries due to poor industrial hygiene practices. Many businesses have no clue about how to monitor air contaminants and keep the air clean.


In Australia alone, around 5,000 cancer cases are attributed to the exposure of carcinogens. Again, as per the WHO, most of these cases are due to poor work conditions and most victims are employees who have to work in such conditions.


This is a concerning factor because on average, a person breathes 23,040 times a day and sometimes only a single breath taken in the contaminated air is enough to cause serious health issues.


The solution to this problem lies in measuring contaminants and hazardous substances in the air so that they can be removed to make the air fresh, breathable and non-hazardous.


There are many types of contaminants that can mix with the air. These include carbon monoxide, sulphur dioxide, carcinogens, asbestos, etc.


Therefore, every industry must take measures to identify these contaminants, measure their presence and take steps to eliminate them to keep the work environment safe.


Types Of Exposure Standards To Know About

Exposure Standard refers to the standard that covers the maximum airborne concentration. In Australia, these limits are set in accordance with Section 17 and 19 of the WHS Act.


This act is about eliminating or reducing the risks that are associated with hazardous substances.


Some main types of airborne Exposure Standards include STEL, TWA, and Peak limitation.


TWA – 8 Hour Time Weighted Average: It refers to a worker being allowed to be exposed to airborne concentration for about 8 hours.


STEL – Short Term Exposure Limit: This involves airborne concentration exposure to be allowed for 15 minutes only. These are implemented in workplaces where air contaminants are clearly identified and are in abundance.


Peak Limitation: This is the strictest Exposure Standard that says that exposure to airborne substances must not exceed 15 minutes at any cost.


However, to determine the right Exposure Standard for a workplace, it is essential to measure the air contaminants first. This is done by taking samples.


There are many sampling techniques that are used to measure the concentration of contaminants found in the air.


Sampling Techniques

Mainly, there are five types of sampling techniques that can be used:


  1. Grab
  2. Short Term
  3. Long Term
  4. Continuous
  5. Bulk


Grab: In this sampling technique, the sample is collected and used for screening. It is important that the sample is collected from different corners.


Short Term: This involves measuring contaminated air for smaller intervals, 10 to 15 minutes.


Long Term: This is done on an 8 or 4-hour time period schedule.


Continuous: Here contaminants are measured continuously to determine the peak time. This also helps find the location of exposure.


Bulk: Not a very reliable technique to collect sample because details can be missed. However, this method can be used to determine asbestos fiber in the air.


These techniques will disclose two things in a work environment:


  • The presence of contaminated air.
  • The concentration of contaminants.


Once these two things are known, further steps can be taken to remove these contaminants from the air.


Sampling is a very important step and must be performed with care. Special sampling equipment is used for this purpose.


Sampling Equipment Required To Collect Samples


occupational hygiene


The following equipment can be used to collect samples.


Equipment Used For Grab Samples:


Detector Tubes: They are easy to use and show immediate results. They work quite like the litmus paper test where the air changes color if contaminants are present. However, they aren’t very accurate.

Gas Sampling Bags: In this technique, pumps are used to collect air. This air is passed into gas sample bags to be sent for analysis. The benefit of this technique is that no air loss takes place as the bag is airtight.


Impregnated Filters Or Paper Tapes: Air is trapped and collected through paper impregnated using chemical reagents. The test works like detector tubes (the air changes color), however one must be quick to notice this change as the stains may disappear quickly.


Electrochemical Detectors: Air is made to interact with an electrochemical cell in this technique. The measurements can be read directly without having to wait. However, it is an expensive technique.


Gold Film Mercury Vapor Analyzer:  Mercury vapors, when inhaled, can damage the heart, kidneys and central nervous system of a person. This is why the presence of mercury in the air is a serious concern.


A gold film sensor is used to measure the air for mercury vapors. The presence of mercury vapors in the air will increase the resistance of the sensor and confirm the presence.


Equipment Used For Long And Short Term Samples


Pumped Samplers (using Charcoal/Tenax): The pump is used to draw in air and the sample is collected in a vessel (tube, etc). This method requires deep analysing using a complex analyzing system. The results are not immediate. However, they are quite reliable.


Diffusive Samplers: Diffusive samplers can diffuse the contaminants in the air using a membrane and expose it on the bed of a filter material. It requires complex analyzing system to measure results. It is a cheap and reliable process but works a little slowly.


Impingers Or Bubblers: In this method, a solvent or reactive solution is used. Air is bubbled into it and the solution obtained is sent for analyzing. However, air loss can take place because of the use of glass vials.


Equipment Used For Continuous Samples


Flame Ionization (OVA or TVA): OVA (Organic Vapor Analyzer) and TVA (Total Vapor Analyzer) are two common types of analyzers used to perform flame ionization. This process is used to measure combustible contaminants in the air.


When air is drawn in, the electrodes sense the hydrogen flame ions present in it, and turn them into voltage signals.


Infrared (Miran Analyzer): Infrared Miran Analyzer is an instrument used to measure air for the presence of various gases used in IR radiation. It can also be used for bulk sampling.


Ultraviolet Spectroscopy: This method is used to measure the presence and concentration of UV rays in the environment.


It is important that the people who use this equipment and analyze samples follow industrial hygiene and wear protective gear and masks while doing their job. Not doing so may cause them to get affected.


Be very careful when selecting a sampling method and choosing an apparatus. This should ideally be done by determining the severity of the risk.


If an area is highly contagious then immediate results are needed and the method which gives the quickest and most reliable results should be used.



The air sample is sent to a team of analyzers. These experts test the sample using complex techniques to find results.


After analyzing, all the contaminants that are present in the air are exposed with details on the concentration of each contaminant.


Merely knowing what contaminants are present is not enough. One should also know the concentration on each to gauge exactly how poor the condition is and what kind of a solution is needed.


This is also important because some contaminants are naturally present in the air and are not dangerous unless they exceed the specific amount. Knowing the concentration can help take the right decision.


Checking And Measuring  Different Contaminants In Air

occupational hygiene


Here are some of the most common contaminants that must be checked for:


Organic Vapors: These are present in almost every industry in some amount, but are most common in paint, cleaning and chemical industries.


To test the air for organic vapors, collect the sample onto a sorbent tube, next provide heat to desorb it or purge it into a gas chromatograph along with FID (Flame Ionization Detector). This method will reveal the presence of organic vapors in the air.


Inorganic Gases: Checking for the presence of different gases requires different methods. CO and CO2 can be determined using the infrared sampling equipment and method. Ozone and oxides of nitrogen can be revealed using chemiluminescence. For sulphur dioxide, microcoulometry and photometric can be used.


Inorganic gases are the most common cause of indoor pollution. They can deteriorate the functioning of the lungs, causing diseases like asthma, bronchitis and cancer too.


Metal Fumes: Simple exercises like welding give rise to metal fumes that can deteriorate the health of people around and the welder as well. Short-term exposure can cause fever, chills for a few hours but long-term exposure can cause diseases like cancer, ulcer, and kidney damage.


To check for metal fumes, collect the air and expose it on a filter paper. Analyze the results using Inductively Coupled Plasma Arc Spectroscopy (ICP).


Asbestos In Air: It is a dangerous cancer-causing fiber that must be checked for in the air. Collect a sample and expose it to cellulose ester membrane filter. Now analyze and look for fibers on the membrane using phase contrast microscopy.


Where To Send Samples For Analyzing?

To PTA Australia because it is a devoted organization for analyzing samples in air.


Methods To Remove Contaminants From Air

occupational hygiene

Several methods can be used to clear the air from harmful contaminants.


Ventilation: There are two kinds of ventilation that can be used to clean contaminated air. These are called Dilution ventilation and LEV.


Dilution ventilation refers to clearing smaller amount of contaminated air by adding fresh air into the room using a large fan, air blower, etc. In this method, the contaminants aren’t removed but the air is diluted to reduce the presence of contaminants.


LEV Ventilation involves removing contaminated air using:


Enclosing Hoods: They capture contaminants from the air and separate them.



Ductwork: Ductwork is used to carry contaminated air from the inlet towards an air-cleaning device. The velocity generation in the duct must be high enough to hold particles within the air stream. It can transfer grinding dust, wood shavings, asbestos, silica, etc., into air cleaners.


occupational hygiene

Air Cleaning Devices: Air filters, dust and fume collectors are air cleaning devices to do the job.


Air filters clean the air using air-conditioning system and ventilation by implementing HEPA filters. HEPA filters are known to clear 99.9% air from particles and allergens.


Fume collectors are much more powerful than air filters but they just extract contaminants from the air and pass them to the LEV system for purification. These include cyclones, fabric filters, wet collectors and electrostatic precipitators.


Removing Mist, Vapors And Gases: Combustion, chemical absorption and condensation techniques are used.

occupational hygiene


Air Movers: They are large fans used to generate centrifugal and axial flow air in a room. Using them, the environment can be cleared from contaminated air by directing it to the ductwork that leads the air outside, in the open.


Final Words

Many organisations employee specialist Occupational Hygienists in house that can help with implementing mitigation actions. Specialists Occupational hygiene consultants like Anitech Consultants can as assist if organisations need external support.

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