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traditional dry heat technologies in which air remains static (air movement only by gravity
convection) or in which air is minimally re-‐circulated by mechanical convection to enhance heat
distribution. Derived from NASA dry heat technology HVHA technology employs directed, uniform
high-‐velocity hot air across the surface of a medical device to enhance heat transfer. As a heat
conduction process, this high velocity, thermodynamic mechanism decontaminates both the surface
and the interior of a device and its components, including residues that may still be retained. The
result is a marked reduction in time required for mask decontamination by traditional dry heat
methods.
The RH-‐Pro11 technology has been repurposed into the RH-‐N95 Mask Decontamination System that
is solely dedicated to N95 mask/respirator decontamination. Using a dual airflow pathway, air
heated to (167°F +0.5°F; 75°C) and is mixed to homogeneity before entering the processing chamber
at a velocity that delivers about 200 air exchanges per minute. The closed air-‐handling system
provides the ability to control and maintain the pre-‐set temperature throughout the entire 34-‐
minute decontamination process. As a dry heat process, only temperature and time are the critical
cycle parameters in this process. The use of a proportional-‐integral-‐derivative controller optimizes
sterilization chamber warm-‐up, more precisely maintains plenum temperatures, minimizes
temperature over-‐ and under-‐ shoot, and speeds heater element response to provide the
temperature control necessary for this process. The on-‐board computer monitors the entire process
and if significant deviations occur from prescribed parameters, error messages are displayed,
delineating the problem. If these errors result in significant deviance of required time-‐temperature
parameters that are required for desired viral or bacterial inactivation levels, the unit will terminate
the cycle, notify the operator of the event, and document the incomplete cycle in the stored data log.
The decontamination cycle for the RH-‐N95 is set for a 30-‐minute exposure at 167°F (75°C), a
relatively low temperature and one that cannot kill bacterial spores nor has an approved chemical
indicator. For monitoring of the mask’s time-‐temperature conditions a better alternative is offered
by placing a thermal sensor logger next to or under a mask during the decontamination process. The
time-‐temperature data is recorded during the process and upon completion of the cycle is
downloaded onto the RH-‐N95’s computer for graphical screen display and internal storage. The
operator is instructed to acknowledge these results before the next cycle can be initiated. The
logger’s data is concurrently stored with the time-‐temperature data generated from the RH-‐N95’s
chamber temperature sensor and available for download to a flash drive for off-‐site storage and
hardcopy documentation, if desired. See Figures 1 and 2 below.
Figure 1
