Test Results

Moistureguard Covers trap over 90% of respiratory aerosols across the instrument range


Dr Alex Parker, PhD summarises the test results below:

The release of respiratory aerosols from instruments has been a key part of the debate about the safety of playing brass instruments. To help collect the evidence needed to bring players back together, we worked with all the partners in this experiment to bring together a group of some top brass players to be able to test both what particles are produced compared to other activities, and what measures could be introduced to help mitigate any risks.


The experiments carried out looked at the number of particles released and showed a mean average of 53,800,000 aerosol particles per meter cubed of air expelled, particularly over extended playing periods of over one minute. When using the MoistureGuard this number was reduced by over 90%, a significant reduction.

There have been a number of recent studies detailing the transmission of SARS-CoV-2 via both droplet and aerosol airborne particle routes of infection. Because of this, it is necessary to understand the release of different size particles in activities such as playing brass instruments in order for a proper 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 material barrier. 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 Aerosol type particles/m3 and 1.43x104 Droplet type particles/m3 per minute. When breathing the mean count was 1.61x107 aerosol type particle/m3 and 5.45x103 droplet type particles/m3. When playing with a barrier cover, the mean number of particles emitted fell to 2.60x106 aerosol type particle/m3 and 5.20x103 droplet type particles/m3.


It was also investigated what effect playing for a more extended period had on the release of particles with comparisons made to singing, breathing and covering the instruments’ bell end with a barrier cap. This showed that the mean number of aerosol type particles produced while playing was 5.38x107 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  aerosol type particles/m3. Both breathing and singing showed consistent numbers of aerosol type particles produced with means of 6.59x107 aerosol type particles/m3 and 5.28x107 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 wind instrument, the propagation of respiratory aerosols does occur and to a smaller extent so do droplet size particles but at a lower level that 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.

How Moistureguard Works

The filter covers we have developed allow sound to travel through the instrument, but trap over 90% of respiratory aerosols and droplets from entering the atmosphere, giving a much safer playing environment, whether this be one to one tuition, school ensemble or bands, orchestras, wind and fanfare bands, brass bands - in fact, any type of musical ensemble that involves woodwind or brass instruments. The covers are fully machine washable and can be tumble dried. The products have gone through controlled laboratory tests to measure their filtration levels. Please see our video above for full details of the trials and players views.