Investigation into the Release of Respiratory Aerosols by Brass Instruments and Mitigation Measures with Respect to Covid-19

Parker, A. S.; Crookston, K.

There are a number of recent studies detailing the transmission of SARS-CoV-2 (Covid-19) via both Droplet and Aerosol airborne particle routes of infection. Because of this, it is necessary to understand the release of different sized particles in activities such as playing brass instruments in order for an analysis of risk to take place for such activities. In this investigation, the quantity and size of particles released by brass instruments while they are played was analysed for 7 different types of brass instrument. This was contrasted with the same individuals breathing as a comparison for more general activities as well as the effect of a mitigating polycotton barrier over the end of their instruments. To investigate the particles released, the particles were size sorted and counted with a six-channel laser particle counter. Multiple measurements were made by each individual in each condition investigated. The mean concentration exiting across all instruments measured was found to be 1.21x107{+/-}1.03x106 Aerosol type particles/m3 and 1.43x104{+/-}9.01x102 Droplet type particles/m3 per minute. When breathing, the mean count was 1.61x107{+/-}1.33x106 Aerosol type particle/m3 and 5.45x103{+/-}1.20x103 Droplet type particles/m3. When playing with a barrier cover, the mean number of particles emitted fell to 2.60x106{+/-}2.11x105 Aerosol type particle/m3 and 5.20x103{+/-}8.02x102 Droplet type particles/m3. This barrier represented an average 78.5% reduction for the number of respiratory Aerosol type particles and 63.8% reduction for Droplet type particles compared to playing an instrument without the barrier covering. It was investigated what effect playing for a more extended period of time had on the release of particles with comparisons made to singing, breathing and covering the instruments' bell ends with a barrier cap. This showed that the mean number of Aerosol type particles produced while playing was 5.38x107{+/-}3.15x106 Aerosol type particles/m3 produced and showed a significant drop in Aerosol type particle production when playing with a barrier used, with a mean average of 2.28x106{+/-}8.01x104 Aerosol type particles/m3. Both breathing and singing showed consistent numbers of Aerosol type particles produced with means of 6.59x107{+/-}7.94x105 Aerosol type particles/m3 and 5.28x107{+/-}5.36x105 Aerosol type particles/m3 respectively. This showed a drop in mean Aerosol type particles/m3 of 95.7% when using a barrier cap compared to playing without a barrier. It is concluded that, while playing a brass instrument, the propagation of respiratory Aerosols does occur and, to a smaller extent, so do Droplet size particles, but at a lower level than when the subject was breathing without an instrument. Finally, it was shown that the use of a barrier cap on the bell end of the instrument offers a significant reduction in the production of respiratory Aerosols into the immediate surroundings, which offers a possible mitigation method for playing in groups from the release of Aerosol type particles, especially in hard to ventilate spaces.