Military weapons platforms and systems are exposed to a wide range of contaminants for various missions. Cleaning and decontamination are commonly performed by labor using a traditional cleaning agent that is “wet-based” such as bleaches like P-D‐680 that is a petroleum-based solvent, which contains hazardous air pollutants and volatile organic compounds causing environmental and health concerns. Its successor, MIL-PRF-680 is also a petroleum-based solvent that contains the same amount of volatile organic compounds (VOCs, more than 750 g/L) but no hazardous air pollutants (HAPs). The aromatic contents approximately 1% by volume maximum, total phenol is no more than 0.5 ppm, dichlorobenzene is 0.5 mg/L maximum, and benzene is 0.5 mg/L max in MIL- PRF-680. Cold solvent cleaning of aircraft components is performed at organizational, intermediate, and depot level and usually takes the form of either spray sinks or batch loaded dip tanks. It is important to remember that the use of these solvents would release large amount of the synthetic organic compounds into the environment. The release could increase the risk of human exposure to the hazardous chemicals, particularly to the decontamination workers. Release of HAPs could also increase the atmospheric burden of organic compounds that might promote the formation of smog and degrade ambient air quality. Non‐compliance of air quality in an air shed surrounding military base or installation could cause undesirable consequences hindering training and other military activities.
The objective of this limited-scope 12-month SERDP project was to explore the feasibility of the technology in dry removal of contaminants. This project aimed to discover how effective the Atmospheric Pressure Nonthermal Plasma (AP NTP) is in the removal of selected contaminants without harming the support substrate and what byproducts may the AP NTP technique produce.
Nonthermal plasma was tested as a decontamination alternative for a number of pollutants in this project. A radiofrequency-powered nonthermal plasma technique was applied to biological aerosols, oil and grease, and paint-stained airframe structural material. Raman spectroscopy, scanning electron microscopy, and aerosol monitoring techniques were used to assess the effectiveness of the plasma decontamination technique.
The conclusions from this limited-scope project study are:
The nanoparticles produced are detectable but can be safely controlled and removed by a high-efficiency particulate air (HEPA) filter.
Use of chemical cleaners can be expensive and cumbersome due to storage and transport. The potential for producing secondary pollution by wet cleaning methods also raises environmental concerns. The nonthermal plasma cleaning technique has several advantages compared to chemical cleaners. The nonthermal plasma technology does not produce residue, and no waste is generated.