  Environmental pollutants are a source for reliability issues across data
center and telecommunications equipment. A primary driver of this is the
transport and deposition of particle matter (PM$_{2.5}$, PM$_{10}$) on printed
circuit boards, electronic components and heat exchange surfaces. This process
is enhanced by turbulent air flows generated from cooling fans. Particle
pollutants can persist after contemporary filtering, highlighting the
importance of elucidating particle transport mechanisms and utilising this
information to design robust equipment. This study investigates particle
transport behaviour arising from axial fans operating under varied aerodynamic
conditions. Transient, multi-phase numerical simulations were performed to
model the flow of millions of microscale particles in air and determine their
fate. Across a comprehensive range of fan operation conditions, from
aerodynamic stall to free delivery, non-dimensional deposition velocities
spanned an order of magnitude. Deposition profiles vary from monotonic to
non-monotonic behaviour, influenced by local flow impingement, blade tip
vortices, and shear velocity. A simple flow control solution that mitigates the
factors influencing deposition has been demonstrated for equipment already
deployed. The findings and numerical methods can be applied for the
optimization of fan-cooled equipment intended for indoor and outdoor
environments where air quality is poor, or pollution levels are high.
