PHYSICAL SPACE AND ENVIRONMENT

There is a need for ensuring an optimal design and layout of the doffing zone, to ensure adequate space in order to dilute the biological infective load, as there can be more than 2 or 3 persons doffing simultaneously after a working shift.^{Reference Wong, Matić and Campiglia10} Apart from being separately located from the donning zone, this zone should have separate access points for HCWs, BMW disposal teams, and the monitor or the supervisor called the “dofficer,” preferably with real-time monitoring.^{Reference Evans, Thomas and Bell11} This zone should have appropriately placed full-body length mirrors, handrails, or sitting arrangement aiding in the doffing of various components of the PPE.^{Reference Wong, Matić and Campiglia10}

The doffing zone should be equipped with a separate air handling unit, negative pressurization, use of 100% fresh flow, a higher number (more than 20) of air changes per hour (ACH) with minimal or no re-circulation, and directed air flow from the clean to dirty zone (preferably laminar pattern) to reduce the concentration of the virus in the air.^{Reference Lockhart, Duggan and Wax8,Reference Saran, Gurjar and Baronia12} ACH can be decided based on the bio-load in the doffing zone, as even up to 100 were considered in walk-through screening centers for COVID-19, which can remove 99.99% of particles in the air within 3 to 5 minutes.^{Reference Il and Lee13,Reference Sparks and Chase14} High efficiency particulate air (HEPA) filters, which have 99.97% filtration efficiency at 0.3 µm sized particles, could be changed to ultra-low penetration air (ULPA) filters, which have 99.999% efficiency for up to 0.12 µm particles as the size of the SARS-CoV-2 virus ranges from 0.06–0.14 µm, especially if re-circulation based air distribution system is used.^{Reference Sparks and Chase14} The heating, ventilation, and air conditioning (HVAC) system relies on “conforming to the path principle,” in order to avoid disturbances to the pattern of air flow by any additional or new equipment or personnel; once all the equipment is set up in the doffing zone and the path of movement of personnel is ascertained, the HVAC engineer should be consulted to look after and adjust the flow pattern and changes to be made accordingly.^{Reference Saran, Gurjar and Baronia12} “Intelligent” HVAC systems which adjust their flow pattern as per the occupants, can also reduce the risk of contamination.^{Reference Reijula, Holopainen and Kähkönen15}

The installation of approved environmental sterilizers, such as an ethylene-oxide (EO) gas aerator cabinet, and disinfectant devices, such as ultra violet germicidal irradiation that either emits continuous ultraviolet (UV-A or UV-C) light or a pulsed-xenon UV light system, photon mediated electron emitters, can reduce the viral load in the doffing zone.^{Reference Nardell and Nathavitharana16,17} In addition, air purifiers (Medical UV air purifier) also have a role in such zones.¹⁷ The efficacy of the above measures should be ensured by frequent air sampling to estimate the viral load with ddPCR or with the index of microbial air contamination (IMA), apart from “filter forensics” at specified time intervals to understand the bioload in such zoning and planning interventions.^{Reference Lockhart, Duggan and Wax8,Reference Saran, Gurjar and Baronia12}

BIOMEDICAL WASTE DISPOSAL

There should be sensor-based or foot-operated large sized covered and clear demarcated bins using high level disinfectant such as 1% Virkon™, accelerated hydrogen peroxide based disinfectant (Oxivir®), when compared to those commonly used in disinfection of high touch surfaces (0.5–1% sodium hypochlorite).^17-19 Separate labeled containers should be available to facilitate disinfection and maintenance of reusable components of PPE like powered air purifying respirators, other high-end respirators, and face shields.¹⁹ Recent advancements include the utility of biosafety cabinet-like systems, labeled “SAFETY,” in the screening zones of COVID-19; the same can be implied to the doffing zone in order to protect HCWs from self-contamination.^{Reference Il and Lee13} Doffed PPE can be kept in biosafety cabinets (BSC Class 2 and above), in which the HEPA-filtered unidirectional air flow pattern is maintained. UV irradiation inside the BSC can further reduce the bioload before the BMW team collects them for disposal. The implementation of robot-based systems or conveyer belts to carry the potentially infective load (discarded PPE) from the doffing zone to the terminal disinfection zone offers an opportunity to reduce further exposure of HCWs involved in BMW management.^{Reference Vaishya, Javaid, Khan and Haleem20}

PERSONAL PROTECTIVE EQUIPMENT

In cases of PPE, while breathability and water vapor evaporation ensure comfort, the use of fabric with Class 3 exposure pressure and above ensures safety and carriage of the least possible biological load.^{Reference Katoh, Tanabe and Kasai21} A notable advancement in fabric design by a team from Indiana University, United States, has been the development of electroceutical fiber PPE, with alternating dots of silver and zinc batteries that can destabilize the virus by the creation of a weak electric field.²² This, and also the use of antimicrobial repellent finishes, can also reduce viral loads in the doffing zone. It is also essential to choose fabrics with adequate tensile and breaking strength, as damaged PPE incurs the risk of “pathogen carry over,” owing to increased microbial adhesion to damaged surfaces, especially during doffing.^{Reference Muñoz-Leyva and Niazi7,Reference Tanabe, Uchida, Arakawa and Morimoto23} Identifying potential self-contamination on PPE, skin, and clothes worn by HCWs using fluorescent tracer methods offers another solution to mitigate this risk.^{Reference Therkorn, Drewry and Andonian24}

HUMAN BEHAVIOR AND COMPLIANCE TO PROTOCOLS

Adequate training and frequent monitoring of HCWs during donning and doffing can limit the transmission of infection, by reducing deviations from ideal techniques.^{Reference Lockhart, Duggan and Wax8,Reference John, Hassan and Weich9,Reference Evans, Thomas and Bell11} Also, it is necessary to obtain frequent data regarding the facilitators (Is this the meaning you intended?like fitting of PPE) for improving the compliance, along with barriers like fogging, perspiration, as evaluated in a recent questionnaire-based study.^{Reference Baloh, Reisinger and Dukes25}

The doffing zone needs extra monitoring by a “dofficer” in real time, in order to ensure the appropriate disposal of used PPE in compliance with the established SOPs in that particular facility.^{Reference Evans, Thomas and Bell11} In a study of assessing common behavioral faults during doffing, Mumma et al. found that the most frequent steps leading to maximal non-compliance involved removing the outermost garment, boot covers, and respirator hood apart from hand hygiene.^{Reference Mumma, Durso and Casanova26}

Ensuring hand hygiene with alcohol-based sanitizers and a minimum contact time of 20 seconds at every step of removal of each item of PPE is crucial.^{Reference Muñoz-Leyva and Niazi7} This could be ensured with the help of audible alarms or music for a requisite duration (20 seconds) after pressing the foot-operated sanitizer systems.^{Reference John, Hassan and Weich9} The use of computer simulations ensuring the proper sequence of removal of PPE, incorporation of alarm systems in case the sequence is failed, and also the use of telecommunication (a supervisor giving instructions to the HCWs through audio-visual interface) can ensure a safe passage of the HCWs through the doffing zone, with minimal self- and cross-contamination risks.^{Reference Wong, Matić and Campiglia10,19}