Opening a new front to the debate whether N95 masks can really offer protection from the novel coronavirus, the Union Health Ministry has warned against the use of such masks with valved respirators, which is basically the raised plastic disk that is embedded in the fibre.
In a letter to all states and Union Territories, the Director General of Health Services (DGHS) in the Health Ministry, Dr Rajiv Garg, said N95 masks with valved respirators do not prevent the virus from spreading out and are “detrimental” to the measures adopted for its containment. “It is to bring to your knowledge that the use of valved respirator N-95 masks is detrimental to the measures adopted for preventing the spread of coronavirus as it does not prevent the virus from escaping out of the mask,” Garg wrote in the letter.
In fact, in May, the San Francisco Department of Public Health had warned of the inappropriate usage of N95 masks. “The ones with the valves or openings on the front are NOT safe, and may actually propel your germs further,” the department had tweeted.
What are N95 masks? How many types of N95 masks are there?
N95 masks are personal protective equipment that protects the wearer from airborne particles and from liquid contaminating the face. The latest government warning is for those N95 masks that come with exhalation valves. N95 masks are worn mostly by healthcare workers and are known to offer the highest level of protection against airborne infections, but they still have limitations. N95 masks filter about 95 per cent of particles smaller than 300 nanometres (1 nm is a billionth part of a metre). SARS-CoV-2, the virus that causes Covid-19, however, is in the size range of 65-125 nm.
What is the function of the valve in an N95 mask?
The valve or the raised plastic gasket found in some N95 mask models basically filters the air inhaled by the person and blocks the entry of pathogens suspended in the air. The valves allow easier exhalation than traditional masks, prevent humidity, reduce heat and carbon dioxide build-up inside the mask.
What is the concern raised by the Health Ministry?
The Health Ministry has stated that N95 masks with valved respirators does not prevent the virus from escaping out of the mask. The valve is basically a ‘one-way valve’ that only protects the person wearing it and doesn’t filter the aerosols coming out. Hence, an asymptomatic carrier of the novel coronavirus can easily spread the infection to others when the valve releases the unfiltered exhaled air in the immediate surroundings. Thus, in a closed area, people around the carrier have a higher risk of potential exposure to the virus. Asymptomatic transmission is when a person who displays no Covid-19 symptoms — such as fever, body ache, cough etc — transmits the infection to another person.
On the other hand, a mask without a valve will not allow the virus to spread.
According to Dr Ajit Kumar Das, the valve becomes a pocket of infection as it is a ‘one-way’ mechanism and exhaled air passes unfiltered into the environment. “The purpose of a mask is not only that it reduces the possibility of the virus getting inside the respiratory tract but also prevents the aerosols from spreading in the surroundings. Through the valve, exhaled air passes unfiltered into the environment and has the potential of taking coronavirus droplets with it, putting others nearby in the risk of contracting the infection,” Dr Das told indianexpress.com.
So, how do you replace the N95 mask?
The Health Ministry has encouraged the public to use home-made face masks or coverings made of cloth, preferably cotton, which can be tied or fastened over the nose and mouth. The government has also issued a detailed manual on how to make home-made masks and recommended it to everyone. The World Health Organisation, in its June revised guidelines, has suggested that everyone should wear fabric masks (non-medical) in public. Fabric masks should contain at least three layers of different materials. Any person showing symptoms of Covid-19 should wear a medical mask.
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