Page 43 - JSOM Summer 2024

The exposures were made at 3 different oxygen concentrations
within the EOB of 25%, 35%, and 45%. Each exposure was 5
seconds representing the standard CEW exposure time of a sin-
gle trigger activation. If ignition was achieved before 5 seconds,
the CEW was manually turned off upon ignition recognition,
and the fire was extinguished. Data collected included oxygen
FIGURE 4 Experimental concentration, combustible material present, and binary out-
oxygen box. come of positive or negative ignition and was recorded in a Mic-
rosoft Excel Database (Microsoft Corporation, Redmond, WA).

Results
Phase 1 Results
Initial oxygen concentration measurements on the exam table
at room air and at the oxygen spigot flowing at “flush” were
A fresh pork shoulder with intact subcutaneous fat and cu- 19.7% and 100%, respectively. The oxygen concentration
taneous skin layers was placed within the box, skin side up, measured within the oxygen mask connected to the oxygen
representing biologic tissue to simulate the surface of a patient. spigot flowing at “flush” rate was 98%. These did not change
Various combustible items were placed on top of the pork in- over time. At distances of 6 inches (15.24cm) from the mask
dividually and in combination to determine ease of ignition in any direction, oxygen concentrations were between 20.1%
(see Figure 5 for the experimental setup). These items were and 31.5%, with the highest reading at the 12 o’clock posi-
a cotton patient gown sample, a surgical paper drape, a 4×4 tion (mask nasal bridge position). The 31.5% measurement
cotton gauze pad, and human hair (collected from a barber). was the highest concentration measured at maximal “flush”
CEW darts were manually placed into the pork at separation rate from any location sampled. Sampling beyond 6 inches
distances of 6 inches (15.24cm) and 1.5 inches (3.81cm). (15.24cm) from the mask in any direction yielded varying ox-
ygen concentration readings never greater than 31.5%. Phase
FIGURE 5 Experimental setup. (This variation shows the CEW darts 1 data are displayed in Table 1.
within human hair set on top of a surgical drape lying over a fresh
pork shoulder.)
Phase 2 Results
Initially, the CEW darts were tested by embedding them within
the combustible items at separation distances of 6 inches
(15.24cm). No electrical arcing effect between darts was
noted, and no ignition occurred regardless of oxygen concen-
tration inside the EOB.
At 6 inches (15.24cm) of dart separation, the lack of electri-
cal arcing between the darts is because the distance between
them is too great. To create a condition favoring ignition, the
darts were manually placed 1.5 inches (3.81cm) apart for the
remainder of the exposures, which yielded consistent arcing.
This is consistent with Paschen’s law which requires a certain
gap distance between 2 electrodes in a gas as a function of
voltage and pressure to create an electrical arc. 11

There were 24 separate ignition attempts made at dart sep-
aration distances of 1.5 inches (3.81cm), with various com-
binations of combustible materials and various oxygen
concentrations present within the EOB. All exposures involved
the pork as the foundation to simulate biologic tissue. Igni-
tion and spontaneous combustion of the materials tested was
unable to be achieved at EOB oxygen concentrations lower
than 45%. At 45%, only 1 of the materials tested ignited and
burned, which was the human hair, and only when the darts
were close enough to allow for electrical arcing. When the
materials were tested in combination at 45% oxygen concen-
tration with arcing present, the human hair would ignite and
eventually lead to combustion of the other materials, but the
other materials did not ignite alone under this condition. Phase
Manual dart placement was: 2 data are displayed in Table 2.
• Embedded to full depth in the pork without any combustible
item overlying (to simulate exposure into bare skin/tissue). Discussion
• Embedded into each of the combustible items (individually
and in combination) overlying the pork (to simulate expo- Combustion is the process whereby fuel undergoes rapid oxi-
12
sure without tissue embedment). dation to produce heat and light. It requires fuel, an oxidizer
CEW Fire Risk with Supplemental Oxygen | 41