Personal Protective Equipment (PPE) Requirement for PAO-4 During Filter Leakage Testing
When the PAO-4 Safety Data Sheet was updated to align with the Globally Harmonized System of Classification and Labeling of Chemicals (GHS), PAO-4 became classified as an Aspiration Hazard under A.10 Aspiration Hazard in OSHA’s Hazard Communication Standard updated March, 2012.
According the GHS classification requirements, PAO-4 is an Aspiration Category 1 Hazard for the following reasons:
- PAO-4 is present at a concentration greater than or equal to 10%.
- PAO-4 is a hydrocarbon that exhibits a kinematic viscosity less than 20.5 cSt (centistokes) at 40 °C
For these reasons, the following health hazard pictogram must be shown:
The above regulation applies when a worker is handling PAO-4 directly in liquid form. This would include decanting or filling an aerosol generator for filter testing. Proper PPE must be worn to minimize worker exposure.
During filter testing, PAO-4 is nebulized and the resulting droplets diluted with air to produce a poly dispersed sub-micron oil mist or aerosol. This step dramatically reduces the concentration of PAO-4 that workers are exposed to during filter testing.
The two most common aerosol generators manufactured by Air Techniques are the Model TDA-4B Laskin nozzle generator and the Model TDA-5B/ATI 5C thermal generator.
For both generators, the greatest PAO-4 concentration is found at the point where aerosol is introduced to the filter system before being diluted by the filter air flow.
In the case of the Model TDA-4B, the maximum concentration is approximately 30.6 milligrams of PAO-4 per liter of air. For the Model TDA-5B/ATI 5C thermal generator(s), the maximum concentration is 2.3 grams of PAO-4 per liter of air. These levels are a total of 0.0031% and 0.23% respectively of the air/oil mixture.
Typical exposure for an end-user, upstream of the filter under test, does not exceed 100 micrograms of PAO-4 per liter of air and is typically between 10 and 20 micrograms of PAO-4 per liter of air. An end-user who is downstream of the filter under test will be exposed to a level of PAO-4 that is typically less than 0.1% of the upstream concentration except in extreme circumstances. This means that the likely maximum exposure downstream is 0.1 micrograms of PAO-4 per liter of air for brief intervals.
As described above, end-user exposure to PAO-4, even at the point where the PAO-4 concentration is highest, is still far below the 10% level stated by the GHS Aspiration Hazard classification.
Additionally, the threshold limit value (TLV) stated on the most current Safety Data Sheet (SDS) for PAO-4 is 5-mg/m3 (5-µg/l). TLV is defined as the level a worker can be exposed to 8 hours a day for a working lifetime without adverse effect.
Based on these values a protective mask or other forms of PPE would not be necessary when using PAO-4 in aerosolized form during filter testing provided the levels remained below 5 mg/m3.