An Assessment of Volatile Odor Profiles from Polymers used in the Fabrication of Ghost Guns

3-D printed firearms, also commonly known as ghost guns, have been increasingly popular over the past 13 years. One of the reasons it has increased popularity is due to these weapons’ untraceable nature. The increasing popularity leads to a growing concern about public safety. The current detection methods used to identify conventional firearms, such as metal detectors and canines, aren’t a viable detection method that can be used for identifying this upcoming threat of ghost guns. Since ballistic examiners can't rely on traditional methods for examining striation marks, as ghost guns don't produce these markings, there is a dire need to explore alternative techniques for analysis. It’s imperative to understand the odor signatures from various polymers and their various brands and colors to possibly add another technique to the ballistic examiners’ toolbox, that could possibly allow for the examiners to create associative links between a crime and a ghost gun. The objectives of this study were to: 1) conduct and analyze the odor profile of various polymers before and after printing, and 2) conduct and compare chemical characterizations of the headspace of a 3-D printed Liberator before and after discharge. This study utilized solid phase micro-extraction (SPME) coupled to gas-chromatography/ mass spectrometry (GC/MS) technique to conduct the headspace sampling of the various polymers and Liberators. For the first objective, the sampling took place using either filament cut directly from the spool (n=10) and 3-D printed polymer blocks (n=10 ) for each of the 5 colors of one brand and two colors of the second brand. For the second objective, the headspace sampling of the Liberator prototype took place before and after the firing discharge. Highly occurring compounds were deemed those present across 7 or more samples across one polymer type and condition (pre-print and post-print). These functional groups of compounds deemed as high occurring included alcohols, aldehydes, alkanes, alkenes, benzenes, carboxylic acids, ketones, and diesters. The odor analysis showed that there were a few unique compounds for the two-brand analyzed during the study. This study will provide a framework for foundational data for odor profiles of various polymers and their respective brands and colors. While there are several studies that have looked at the health effects of volatile emissions during 3-D printing processes, there is a lack of studies that have chemically characterized common polymers used for ghost gun manufacturing using headspace sampling techniques. This study attends to a research gap by using SPME-GC/MS to evaluate odor profiles of various polymers before and after print, as well as before and after discharge of a 3-D printed firearm to combat an evolving national security threat.