(W0930-09-59) Pneumatic Aerosolization of the Surrogate Acetaminophen in a Newly Developed Chamber Setup for Containment Investigations with Special Focus on Spatial Dust Distribution

Purpose: The present study deals with the aerosolization of the surrogate acetaminophen (ACAM) by directing compressed air through a double acting ball valve of a novel chamber setup for the examination on dust formation in the context of Containment. In a previous study the evacuation time required to collect the entire content of the detection chamber was determined with the fume of sulfuric acid as a model aerosol. Based on these results the parameters for detection as well as emission of ACAM were kept constant. The only variable was the sample weight used for aerosolization. The totally settled amount of ACAM in all 9 IOM samplers (Institute of Occupational Medicine) was quantified.

Methods: The experimental setup consists of two chambers, the emission and the detection chamber which are connected to each other (Fig. 1). The dimensions of the chambers are specified in a previous publication. The sample of ACAM is transfered into a small tube above the double-acting ball valve. Subsequently, the 5/2-way valve, controlled by a programmable logic controller (PLC) opens the double-acting ball valve positioned above the emission chamber (Fig. 2). By this means, compressed air with a preset flow rate of 100 l/min is directed through the double acting ball valve for 5 s the sample is thereby aerosolized and introduced into the emission chamber. Simultaneously, the 3/2-way valve between the sampling pump and the 9 IOM samplers in the detection chamber was activated leading to an airflow of 2 l/min through each of the samplers. Via convective and diffusive mass transport the aerosol passes through the connecting orifice from the emission to the detection chamber and eventually settles on the filters within the 9 IOM samplers. The amount of ACAM settled on the filters was quantified by HPLC.

Results: The results of the pneumatic aerosolization with varying sample weights ranging from 65 to 1000 mg are shown in Fig. 3. The lowest settled amount of ACAM recovered from all 9 IOM samplers is found at a sample weight of 65 mg and the highest amount at a sample weight of 1000 mg. The results show an exponential correlation between sample quantity and settled amount with an r² value of 0.9954. The correlation is not linear, although the energy introduced into the system via compressed air is constant. However the amount of sample on which the compressed air acts was varied. Thus, in the case of small sample quantities, more energy is available for aerosolization per fraction of powder sample.

Conclusion: The present study demonstrated that the newly developed chamber setup is capable of reproducible aerosolization of a surrogate powder. An exponential relationship between the amount of sample applied to the totally settled amount of ACAM within the 9 IOM samplers was demonstrated. Future investigations will show where the process optimum is located with respect to the sample weight, the flow rate of compressed air and the duration of aerosolization.

Fig. 1: Simplified illustration of the novel chamber setup for investigation of the spatial dust distribution.

Fig. 2: Simplified piping and instrumentation diagram of the chamber setup.

Fig. 3: Settled amount of ACAM within the IOM samplers (total of all 9 samplers, means ± SD, n = 3).