Occupational Safety and Environmental Measurement Parameters Air Quality Measurement Parameters and Measurement Methods

One concept frequently encountered in professional life is Industrial Hygiene. In this article, we address the scope of Industrial Hygiene and the characteristics of airborne contaminants within this context. Please refer to our other articles for information on additional components of Industrial Hygiene, such as noise, thermal comfort, lighting, vibration, and electromagnetic pollution, as well as the methods and protocols used to measure these parameters.

What is Occupational Hygiene? Occupational Hygiene: A scientific discipline aimed at anticipating, recognising, evaluating, and controlling conditions that compromise worker health, leading to illness or accidents. Examples of conditions compromising worker health include air pollution (dust, gas), noise, vibration, thermal conditions, inadequate lighting, electromagnetic pollution, radiation, etc. Occupational Hygienist: Identifies and applies necessary methods and standards to conduct assessments in the field of occupational hygiene. What are Air Pollutants? We can classify air pollutants by type as dust, fume, soot, gas, vapour, and fibre (asbestos, etc.).

Let us define the air pollutants we will focus on in this article; AEROSOL: The general term for liquid or solid particles suspended in ambient air. DUST: Small solid particles. Dust can be generated by pulverisation or grinding of solid matter, or through any other mechanical process. Large particles can be cleared by the respiratory system. Examples of mechanisms of action include: lead dust causes systemic damage via the bloodstream; grain dust causes dust explosions if it reaches a specific concentration. Coal dust can be cited as another dust with an exceptionally high explosion potential. If coal dust accumulates above specific concentrations, it leads to explosions. As a precaution, inertisation with rock dust is applied. This inertisation process can be measured using the CDEM-1000 Coal Dust Explosibility Meter developed by Sensidyne.

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FIBRE: Briefly, it can be defined as solid particles whose length exceeds their diameter. Large fibres are cleared by respiration, whereas fine fibres irritate the lungs. A typical example is asbestos fibres. Whilst asbestos sampling and analysis is a comprehensive subject in its own right, sampling can be successfully carried out using Sensidyne Gilian pumps.

Please click here for Sensidyne’s Gilian BDXII pump, used specifically for Asbestos and Heavy Metal Sampling.

Exposure Limits, General Approaches Permissible Exposure Limits (PEL) vary depending on the substance of exposure as well as across different standards. Examples of these international standards include ACGIH (American Conference of Governmental Industrial Hygienists), NIOSH, OSHA, etc. Exposure limits are determined based on exposure durations;

STEL (Short Term Exposure Limit): Short-term exposure limit, based on a 15-minute exposure.

TWA (Time-Weighted Average): Time-weighted average, based on an 8-hour period.

TLV (Threshold Limit Value): Threshold limit value, taking shift-based exposure into account.

Sampling and Measurement Methods Under international standards, two fundamental methods are applied for air pollution and resulting exposure measurements: 1. Gravimetric Sampling Method This method is based on drawing air (sampling) with an appropriate sampling pump, and determining the contamination in the aspirated air directly by gravimetric weighing or analytical methods. When selecting a pump for this purpose, considering several key criteria is essential. These criteria include: the pump having a wide flow range, the ability to switch between high-flow and low-flow without requiring additional adaptors, maintaining stable flow throughout sampling, and not exceeding a deviation of +/-5%. Considering that dust loading in sampled environments can restrict flow, it is important that the pump easily overcomes this resistance with high back-pressure capability. The Gilian GilAir Plus can be cited as an ideal pump for these applications. Please click here for the Gilian GilAir Plus, launched as the world's premier pump used for both dust and gas sampling by Sensidyne.

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The most critical point in applying this method is the sampling heads used for air sampling. If dust sampling is to be carried out, a filter suitable for the sampling environment and dust type must be used. Filters can be selected based on factors such as static electricity, moisture sensitivity, chemical incompatibility, etc. In occupational safety studies, both ambient dust and exposure measurements are performed; however, exposure measurements must take priority. Therefore, exposure zones must be taken into account during sampling. Examining the relationship between inhaled dust fraction size and exposure zone reveals the following data;

Inhalable (upper respiratory tract): Particles of 100 microns and below

Thoracic (middle respiratory tract = chest): 10 microns and below

Respirable (deep alveolar region of the lungs): 4 microns and below

As can be seen from this, as dust particle size decreases, the hazard to worker health increases. Therefore, taking inhaled dust fraction size into account in sampling is critical. The primary accessory used for this purpose is the cyclone sampling head. Cyclone Dust Sampling Head Flow rate may vary depending on the type of Cyclone Dust Sampling Head; e.g. 1.7 L/min is optimal for the Nylon Cyclone Dorr-Oliver. This flow rate is determined based on the optimum flow to separate the targeted 4-micron respirable dust. In certain circumstances, sampling over shortened durations may be required, running at a flow rate of 4.0 L/min using dedicated cyclone sampling heads. All flow rates must be set according to NIOSH or the applicable standard. Click the product link for the Cyclone sampling heads shown as examples in the image and much more. IOM (Inhalable Dust Sampler) Dust Sampling Head If ambient dust or inhalable (upper respiratory tract) assessments are to be conducted, the most suitable accessory is the Inhalable Dust Sampler head, abbreviated as IOM. The ideal operating flow rate for these samplers is 2.2 L/min. The sampling head flow rate must be calibrated in accordance with NIOSH or the standard used. Click the product link for the IOM (Inhalable Dust Sampler) sampling heads shown as examples in the image and much more. Other Air Sampling Accessories If sampling is to be conducted for the measurement of VOCs (Volatile Organic Compounds) and other toxic gases, sorbent tubes, passive samplers, impingers, and similar collection media appropriate for these analytes can be used. Click here for all Occupational Safety Air Sampling Accessories. As NOVEL, we supply and distribute gas and dust air sampling apparatus. Air Sampling Pump Flow Calibrators Another key component in the Gravimetric Sampling Method consists of verification apparatus, rotameters, and Primary – Secondary Flow Calibrators, which ensure measurements are performed professionally and enable flow rate calibration. Flow calibrators are reference instruments that must be used to verify the flow rate of the pump used in sampling prior to operation, adjust for any drift, and re-check post-sampling to demonstrate that the sampling was completed within the specified flow range. Click here for information regarding the Air Flow Calibrators shown as examples in the image.

Flow calibrators are divided into primary and secondary standards according to their accuracy. Primary flow calibrators should be used for flow verification and calibration of sampling pumps. However, the use of secondary flow calibrators in field operations is also accepted. 2. Light Scattering Method for Air Sampling Under certain operating conditions and environments, direct-reading instruments displaying instantaneous measurement results can be used in place of the time-consuming and costly procedures of the gravimetric sampling and measurement method described above. The method utilised in these instruments is termed Light Scattering in international literature. At first glance, one might question why the lengthy gravimetric method is used when instantaneous, direct reading is available. To address this query, let us briefly examine the Light Scattering method; Air entering through the inlet of an instrument operating on this system passes through an optical cell fitted with a specialised lens. As the air flows through the cell, dust particles pass in front of the lens. The optics perform a "mass weighting" based on particle size and count. The algorithm for this mass weighting operates as follows: the instrument is factory-tested against a specific reference dust. First, a gravimetric dust measurement is performed using this reference dust, and the reading displayed on the instrument screen is recorded. The ratio between the gravimetric measurement value and the displayed value is determined, from which a K-factor is calculated to calibrate the display reading to the gravimetric value. This K-factor is configured in the instrument. In this way, the screen reading is corrected against the gravimetric measurement value, bringing both into alignment. When conducting measurements with the instrument in similar dusty environments, this correction procedure does not need to be repeated; selecting the pre-configured K-factor is sufficient. Note: The most widely used reference dust globally is Arizona Road Dust, designated as ARD in technical literature. (Please see What is Arizona Road Dust) However, if the dust profile in the measurement environment differs substantially from the initially selected dust profile, the above procedure is performed once again, and an individual K-factor is calculated and saved. When subsequent measurements are carried out in the same dust environment, correction is applied using this new K-factor. If this gravimetric correction is omitted, the reliability of results obtained from the measurement will be compromised. Due to this requirement for additional processing, this method is not widely adopted for accredited compliance testing. Nevertheless, this method offers substantial advantages and applications: when long-term measurements are conducted using this method in environments with relatively stable dust profiles, logged data can be downloaded to a PC for data analysis. Consequently, temporal and spatial variations can be tracked graphically, identifying specific intervals and moments during the day when dust concentrations increase, decrease, or reach peak levels. This gathered intelligence provides crucial data for preventative control measures in the workplace. Ambient particulate concentrations can be monitored instantaneously with Environmental and Ambient Air Quality monitors supplied by TSI. Ambient Air Quality monitoring can be readily carried out with these technologies utilising various implementations of the Light Scattering method. You can click this link to view these instruments and explore their technologies.

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Associated with this objective, there are instruments capable of measuring not only dust but also other parameters depending on their specifications, such as temperature, relative humidity, total VOCs, CO2, and airflow. Monitoring workplace air quality can be exceptionally straightforward and rapid with these combined instruments. A prime example of such instruments is provided by TSI: EVM Air Quality Monitors and Particulate Measurement Instruments. In addition to industrial monitoring, these instruments are widely utilised in office environments and similar spaces for occupational comfort assessments. In summary, if a healthy working environment is targeted and preventative measures for worker safety are prioritised, the initial step towards these objectives is conducting measurements using correct methods and appropriate instrumentation. In this article, we have outlined the definitions of occupational hygiene components and dust-related parameters within this scope. In our subsequent article, we will address other measurement parameters. Author: Hamdi YÜKSEL All text and visual content on our website belong to the authors of www.novel.com.tr. No content on the website may be copied, modified, or utilised in other print or digital media (websites, blogs, magazines, books, etc.) without written permission. Our rights are protected under the provisions of the Law on Intellectual and Artistic Works No. 5846. Note: All images used may be subject to copyright by their respective owners. Images fall under the “Creative Commons” (CC0) licence.