GRAVIMETRIC AIR SAMPLING

 

Air quality assessments help to quantitatively evaluate the fraction of harmful material in the air. In many industries, this may be a legal requirement to ensure standards are being met or to determine the effectiveness of control strategies.

Employers must take all steps possible to protect workers from exposure to health-harming substances. Any breach of safety regulations can have a major impact on labour effectiveness and places the employer at risk of grave legal consequences. Most government agencies have established ceiling values and guidance limits for a range of harmful gases, vapours, radionuclides and dusts. In the UK, a list of Workplace Exposure Limits (WELs) and occupational standards is downloadable for free on the HSE website (E40/2005). This document is legally binding; non-compliance will result in major penalties.   

Gravimetric air sampling is thought to be the most accurate method of determining particulate mass concentration, as they are capable of sampling at the very lowest detection limits. A sample is taken by drawing a measured volume of air through a collection substrate, which is then sent for further analysis. When sampling gravimetrically, the airborne concentration of a particular substance is calculated by assessing the analytical result and the volume of air sampled.

Types of Gravimetric Air Sampler

The type of air sampler used depends on the size of the area and the duration of the sample. Fixed-point samplers (also known as area samplers) have high flow rates, meaning large volumes of air can be sampled in a short space of time. These are useful for pinpointing the source of contamination and for assessing the effectiveness of control measures.

To monitor personal exposure, a smaller, wearable sampler may be used. These are attached to the operator, and a sample is taken during normal working activity. The sampling head is located in the worker’s breathing zone in order to measure how much particulate matter is inhaled.

For both types of sampling, different filter paper can be used depending on the test parameters.

Although real-time monitors can be extremely useful for initial assessments, they may not be sensitive enough to detect background levels when the concentration of a pollutant is very low.

Munro Instruments specialises in the manufacture of high-quality environmental monitoring equipment. Our comprehensive range of air samplers cater for all environmental and health-and-safety requirements and can be found in nuclear, construction, transport and agricultural facilities around the world.