Ask the experts: How are advances in filter technology improving health and safety?

Scott Health and Safety’s Matthew C. Middlebrooks explains how through the use of new materials, increased technical understanding and improved test methods, they are providing an ever-expanding array of tools directed at the health and safety of workers.

We are constantly looking for new raw materials that will allow us to provide more value to the customer. The latest technology advance is in the area of nanotechnology. Nano-materials are being investigated in both the removal of particles (dust, microbes, etc.) and gaseous contaminants.

Fibre producers are now able to produce man-made filaments with diameters much less than one micron, providing much more surface area per unit mass for removing small particles from an air stream. These nanofibres are exceptionally good at removing the smallest, most penetrating, particles. A thin layer of nanofibres can be added to traditional particle filtration media to substantially boost the filtration efficiency with minimal increase in resistance. In addition, additives or coatings can be incorporated to kill microbes and other organisms that are captured and retained by the filter media.

For gaseous contaminants, nanoparticles and nanomaterials are providing new catalysts and reactants that are effective at room temperature. This is critical for respirators since we cannot use the high temperatures normally required for catalysts. It has been found that many routine bulk materials and compounds exhibit completely different properties when reduced to nano-proportions. They can become much more reactive or produce reactions at much lower, even ambient temperatures. When these nanoparticles are present in a chemical coating or on a carrier particle they can be used as sorbents for hazardous contaminants that were once difficult to remove.

By using these new materials in the optimum ways and in the appropriate applications we will be able to supply respirator filters that are effective against more contaminants and with higher efficiencies than ever before.

Technical understanding

Besides using new materials, we are learning more and more about the performance of our products in the situations where our customers use them. Through the use of theoretical models developed from industry and university research and empirical lab testing, we are learning how to better predict how respirator filters will respond in different situations.

We are continuously updating our database of empirical lab results to understand the impact of various use parameters on the filtration efficiency and life of our respirator filters. We are testing with various contaminants, temperatures, relative humidities, flows, concentrations, and pre-conditioning to anticipate a wide variety of applications and uses. In combination with theoretical modelling of gas adsorption and the flow dynamics of particles, this data allows us to predict filter performance in real-world situations. This is the information needed for EH&S resources to determine change-out schedules for respirator filters to protect workers from both acute and long-term hazards. The better and more detailed the information, the more effective the program.

Test methods and standards

Additional research is being funded by industry trade groups and government agencies studying the interaction between the user and the protective equipment during use. This research is helping to develop test standards and methods that better approximate the way respirators and respirator filters are used by workers. This will lead to more reliable data and predictions and eventually to better filters as manufacturers design to the improved standards.

One of the key factors in the performance and life of a respirator filter is the user themselves. Anthropometric studies are currently looking at variations in breathing patterns of different users within the population. These studies are documenting how the volume, frequency, and shape of the inhalation curve change depending on the fitness and work load of the user within controlled work categories. Real world studies are correlating these work categories to actual job activities. These changes in breathing will affect the instantaneous velocities and load of contaminants that the respirator filter will be exposed to. This information is on top of the known impacts of the broad range of environmental temperatures and relative humidities in which users operate.

Once these effects and variations are known, methods and procedures can be adapted to approximate the various work environments under controlled conditions in a lab setting for certification and prediction purposes. Projects are already in progress to evaluate the impact on respirator filter life of constant flow testing versus using various breathing machines. Data has already been collected on the impacts of temperature, relative humidity, and overall flow rates.

In conclusion, the combination of new materials, improved technical understanding, and better standards will provide users with respirator filters that have better performance against a wide array of contaminants adapted to the particular user applications.