Uncovering the myths behind masks
Respiratory protection has been used routinely in thousands of workplaces in New Zealand to protect people from a wide variety of airborne contaminants, though its use in the health sector against coronavirus is a relatively new application.
There are many myths and misunderstandings about the use of RPE (respiratory protective equipment).
The airborne spread of coronavirus is a significant means of transmission for the general public and healthcare workers. The transmission path is well established, and consists of a range of droplet aerosols of many sizes, some of which can remain airborne for many hours, if not days. The method of transmission has implications for protecting people by various means, including respiratory protection.
When people breathe, sing, and cough or sneeze, thousands of droplets of all sizes become airborne. In a typical sneeze, more than 40,000 of these are spread widely and at quite a speed and distance from the infected person.
The range of particle size can be large, and the larger ones will fall quickly to the ground under the effect of gravity. But smaller micron-sized aerosols may remain airborne. The large droplet advice, which is appropriate, relates to distancing of two metres and washing hands.
There have been numerous recent articles about the wearing of masks, some of which are homemade. It is important to distinguish the function between ‘‘masks’’ such as these and ‘‘respirators’’.
Respirators are designed specifically to protect workers against airborne hazards, and have to be certified by laboratories in several countries. This means they will retain a predetermined percentage of small particulates at given simulated breathing rates.
Masks and surgical masks are not respirators, and are not generally designed for the same purpose. Most surgical masks, for example, are designed to retain large droplets, blood aerosols or small bone fragments, as might occur in a medical setting.
They are not designed for the protection of people from airborne bacteria or virus particles, which will simply pass through the mask because of their small size. They are useful in limiting the spread of large particles from an infected person.
Respirators may appear to be simple devices, but have to be worn under trained and educated conditions – that is, people have to be taught how to fit them, taught their limitations and, in particular, have to be tested for face-fit to ensure that leakage of the contaminant does not occur through the seal.
This method of closely fitting the respirator to the face is routine in most industry sectors where RPE is worn. Not every person fits the same respirator, so the verification of the face seal becomes important. It is a simple test, but an important one.
The normal RPE generally recommended as a minimum requirement is the N95 (or similar to P2 in NZ and Australia) respirator. These are known as ‘‘negative pressure respirators’’, as the wearer has to draw in air through a filter. They are normally supplied as disposable or halfface, which cover the nose and mouth. There are many manufacturers, types and sizes to fit individuals. Facial hair prevents the seal being achieved between the face and the respirator, so men need to be clean-shaven.
A more advanced and better respirator is the Powered Air Purifying Respirator, which appears to be popular and increasingly used overseas, for good reasons.
With these the eyes, nose and mouth are protected, and only filtered air is delivered. The air is generally sourced from behind the person, rather than in front. It is less tiring for the wearer, because air is delivered, rather than drawn through a filter. It can be fitted with P3 filters (99 per cent retention of particulates), can have communication devices fitted, and is easily cleaned.
Approved respirators are certified equipment to protect people from large and small airborne particulates or aerosols. Respirators should be worn by people who may come into contact with infected people in different settings, or in a range of other activities where good protection is sought.
Perhaps now is a good time to prepare for any future situations that may also arise.