Coronavirus and wildfire particles are in the air: Elastomeric N95 (eN95) can help
By Devabhaktuni Srikrishna, MS
Firefighters and other public safety employees need off-the-shelf technology that reliably filters out Coronavirus and wildfire particular matter (between 0.25 and 5 micrometers) both inside and outside the fire station to make a safer working environment. A reusable, and often more comfortable alternative to the disposable N95 is elastomeric N95 (eN95).
Fire fighters across the US are experiencing the spread of Coronavirus (Covid-19) both from outside and within the fire station from their fellow firefighters. At the same time, the lightning fires in Northern California are causing release of particular matter into the air we breathe. When we spoke to firefighters across the state including San Francisco and San Jose, they indicated that they use disposable N95 masks on calls in which they suspect infectious disease, but not while in the fire station with colleagues.
Survey data in July from 4000 first responders with respect to their usage and thoughts about face masks revealed that about 8 out of 10 are required to wear a face mask when interacting with the public, but only 1 in 2 are required to wear a face mask while inside a building or in a vehicle with a colleague, and only 1 in 3 are using a department-issued N95 mask. This is very surprising considering that Coronavirus can spread from person to person without any apparent symptoms and spread through aerosols which can pass thru cloth masks.
The Anaheim fire department was following a similar policy to many departments until two of their fire captains were hospitalized with Coronavirus in the ICU and had to fight for their every breath, after which Anaheim firefighters started wearing PPE even in the fire station. This narrow use of PPE left them vulnerable to Coronavirus spread from firefighter to firefighter within the department as recently also reported in San Jose, Los Angeles, Long Beach and also the Tuscon 911 call center. The Golden State is overwhelmed with Coronavirus, and the state’s health secretary suggested Californians may need to do their own contact tracing. Overall the fall/winter could be one of the most difficult on record says the CDC director.
How does Coronavirus spread?
Coronavirus is believed to primarily spread via air according to the CDC and European CDC. Although some go so far as to say spread via surfaces maybe less significant, it cannot be ruled out. Hygiene from surfaces (hand hygiene) is still considered necessary. However it’s clear that a focused and determined effort to stop contagion from the air is a must-do for high-reliability organizations such as fire departments.
Coronavirus can linger in the air for hours. Although there has been debate whether aerosols contribute to the spread, there is a great deal of variation (see Figure 2) in the amount of virus exhaled by each infected person. One study found that a greater amount of replication competent virus was exhaled in aerosols than droplets. Viable virus has been isolated from air samples collected 6 feet to 15 feet away from the patients.
Several instances of “super spreading” (i.e. individuals who are super contagious) have been documented with Coronavirus. On well-known example is a choir in Washington State which was through the air, another through recirculated air conditioning, and a third with several employees at a call center. Varying numbers (between 30% to 90%) of those who infect others are observed to have no symptoms and some of the maybe super spreaders (asymptomatic super spreaders), meaning you won’t even know if someone in front of you who looks perfectly healthy can be infecting you. In a recent study, levels of virus in those infected with and without symptoms were similar.
Why not just wear “a” mask?
Although the CDC recommends cloth masks, there is a high degree of variance between different mask materials in blocking the virus. Some commonly used masks do not appear to block the virus at all. Fit also matters. Without fit that forms a facial seal even the best filtration material is ineffective. Typical cloth masks are known to block droplets (e.g. > 2.5 microns) but they do not block the aerosols (e.g. < 2.5 microns) that carry the virus. Recently I joined 73 public health experts to write an open letter advocating for innovation in better masks for the public that block the fine aerosols to the same level as the N95 masks used by healthcare workers.
Why go through the effort of wearing N95 masks inside the fire station?
The main reason is that Coronavirus is highly contagious via the air and highly contagious people may not have any apparent symptoms.
We spoke with San Francisco firefighters and learned that current use of N95 is for a very limited range of circumstances. When people can be contagious without symptoms, N95 protection needs to be used continuously both in the community as well as in the fire station.
We can start to think of Coronavirus more like carbon monoxide that spreads throughout the fire station than droplets that are only expelled from a sneeze or cough. Exposure depends on time and distance. The longer or closer you are exposed the more chances are of catching it. Perhaps people can even catch it during sleeping in proximity to others.
Disposable N95 are reserved for medical use and subject to supply limitations. Whereas elastomeric N95 (eN95) remains available off-the-shelf (no apparent supply or usage constraint) and they are better in that they can more easily form a tighter seal with the face without needing adjustment (less room for inadvertent user-error). In a recent study comparing eN95 to disposable N95, the authors reported that the cost was, conservatively, 10 times less per month than disposable N95s after more than 1 month of use no healthcare workers wanted to return to disposable variety. When used consistently eN95 masks save lives.
To enhance readiness of the firefighting force by reducing the likelihood of inhalation of Coronavirus or wildfire particulates while at work in the fire station, and we recommend the following immediately-implementable and low-cost measures:
- Use of elastomeric N95 (eN95) masks that are reusable, off-the-shelf that are tested and approved by NIOSH for continuous protection whenever in proximity of other fire fighters or the public or whenever exposed to wildfire pollution
- HEPA air cleaners within the fire station where fire fighters spend most of their time such as sleeping quarters and common areas.
Elastomeric N95 (eN95) masks are available off-the-shelf that offer much better fit and filtration than typical cloth masks that are needed to protect against Coronavirus carried in droplets and aerosols. Recently I ordered and tried out three models of elastomeric (“stretchy”) masks online from different manufacturers and found them fairly comfortable to breathe in for extended periods of time: the 3M with filter sold separately and Envomask which are NIOSH approved and O2 which is not NIOSH approved. There are numerous other manufacturers and models of elastomeric masks available. These cost approximately $40 to $80 each, and they are reusable, needing filter swap-outs depending on usage and environment (e.g. every 2 to 4 weeks) which cost between $2 to $15 each.
With respect to breathability, I was able to climb three flights of stairs and bike up San Francisco’s hills wearing eN95. Due to the “stretchy” material that adapts to the shape of the user’s face (gel, rubber, silicone) to form the seal, eN95 masks are simpler than a disposable N95 mask that typically uses an adjustable nose bridge to form the face seal leaving room for user-error. These particular elastomeric models shown above have one-way valves designed for easier breathing that are useful in private workplaces where everyone is wearing them. They can be easily modified to block these one-way valves and make them useful in public to meet the requirements of cities like San Francisco.
At fire stations, air cleaners with HEPA filters also help clean the air indoors. Although their effectiveness varies based on numerous factors, we have tried out at least two models (Honeywell and Coway) that operate unnoticeably to offer additional protection that continuously filters out viruses in areas of the fire station where fire fighters spend more than a few minutes of their time e.g. dining areas and sleeping quarters.
Next steps for fire departments
Fire departments need to create a task force to identify requirements and use cases, evaluate commercial off-the-shelf options, and procure eN95 masks for use by their firefighters. Procuring reusable eN95 masks (elastomerics) would not interfere with supply of disposable N95 respirators for medical workers. When procured in larger quantities to meet city-specific requirements, the cost will most likely be significantly discounted than the $40-$80 retail prices discussed above. The City of San Francisco for example is already paying for Coronavirus testing of fire fighters (for free) regardless of symptoms which can be subject to lengthy delays. For the cost of less than one test at $100, the city could provide an eN95 mask to each firefighter that could prevent future infections for months. Procuring, recommending, or requiring eN95 masks (elastomerics) for non-medical essential workers would not interfere with the priority of getting disposable N95 respirators for medical workers. Additionally fire departments may also consider procuring HEPA air cleaners for common areas within fire stations.
Why not just test our way out of this?
Testing is not a panacea. The US Army and the special forces experienced outbreaks in training camps after trainees had already been being tested multiple times. Tests are estimated to have a 30% false negative rate and in at least one study virus has been observed in exhaled breath (not typically tested for) when it was not detected by a common swab test. Testing for essential workers is free in San Francisco but still unavailable in many cities and will not be for at least several months. Although furious efforts to make testing frequent, fast, cheap, easy are underway they are unlikely to materialize for months in the best case scenario. The NIH ran a competition for scalable testing that is only expected to deliver several hundreds of thousands of tests per day in a country of almost 400 million people.
What not just wait for a vaccine?
Vaccines may be unavailable to most people by end of 2020 and perhaps reach a wider percentage of the population by end of 2021, and even then it is expected to offer partial protection.
What about other viruses?
There are over 180 human viruses besides Covid-19, and two new ones discovered each year. Annual influenza is also a respiratory virus. There is a concern that viruses that affect animals could mutate and crossover to humans to become more contagious and deadly. In addition to the ability of non-state actors to engineer and modify viruses to be a WMD (weapon of mass destruction) is becoming easier. Vaccines and tests for Covid-19 will obviously not help with other viruses, whereas investments in reusable N95 masks and HEPA air filtration systems would remain useful tools to prevent respiratory transmission from all these novel viruses beyond Coronavirus.
About the author:
Bio: Devabhaktuni Srikrishna is the founder of www.patientknowhow.com, which curates patient educational content on YouTube. He worked with Dr. Ranu Dhillon to advise the president of Guinea and help manage the country’s response to the Ebola epidemic. Previously he was founder/CTO of Tropos Networks. Tropos makes reliable, metro-scale wireless mesh networks using Wi-Fi for municipal public safety (police/fire/ems), public access, and electric utilities. He holds a BS from Caltech (Math), and a MS from MIT (EECS) and has published works on wireless networks, parallel computer architecture, quantum computing, nuclear security, and controlling infectious disease. In 2014, he was drawn into the unfolding Ebola crisis due to open panic expressed by public health agencies. In collaboration with public health experts, his research on how to control Ebola quickly ended up in the Lancet. This led to the design of the national Ebola response in Guinea where the epidemic began. Subsequent research (below) has been documented on how to control widely spread viruses without access to vaccines and treatments.
Follow him on Twitter at @sri_srikrishna. Email: email@example.com
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