N95 respirators for single-use are important to protect airborne particles and affected patients, but deficiencies during outbreak of disease and other crisis situations can occur. Practices for easing shortages are used to wear N95 breathing for hours or repeated breathing. These activities can differ widely in the different locations and can quickly evolve during a crisis. The findings of this study are not meant as support for practise or as a call for action. Instead, it seeks to provide realistic advice on the possible hazards and benefits to be weighed by clinical centres, during decisions on the reuse or expanded usage of N95 respirators.

The safety assessment of N95 reuse and extended use during critical shortages is not available in reported clinical trials, so we have reviewed 21 laboratory studies because they provide a reasonable basis for behaviour during a crisis. In the event of significant ethical and logistical obstacles the clinical trials are possibly unworkable because of the intermittent, impredecible and complex crisis situations associated with N95 reuse / extended use procedures. Nevertheless, limited laboratory studies show that the preference of extended use over reuse is provided since N95, when targeted and tamed, may readily spread infection and are likely to reuse mechanical faults. Studies of more than 30 N95 respirator models showed the lack of a clinically relevant impact on respiratory effort and gas exchange in respirators with surgical masks. Decontamination of N95 respirators by steam, disinfectants or ultraviolet germicidal irradiation can be safe, efficient and effective in certain settings. The studies available support N95 priority extension over recycling because:

  • There is a high, but low, chance of pathogen transmission from N95.
  • FDA-cleared N95s suffered a mechanical breakdown with just a few reuse.
  • It is unlikely that surgical masks or similar disposable covers over N95s will lead to serious effects during prolonged usage.
  • Commonly efficient method of disinfection, with some loss of filter efficiency, can achieve proper disinfection.


The N95 filters have been tested and approved by NIOSH in the United States. In addition, the FDA controls Class II medical respirators of N95 that are excluded from 510 premarket notification according to the MSH, ONT and ORW product codes. In Europe, FPP2 respirators are the closest equivalent to N95, needed for 94 percent particular elimination above 0.6 um to obtain the CE label.

N95 Extended Use and Reuse 

The N95 breathing machine shall be discarded at each meeting or phase involving the breathing machine; the breathing machine shall be deemed to be a potentially biohazardous waste and shall be disposed accordingly. Nevertheless N95s are built to operate for days or weeks at breathing-compatible airflow speeds, and theoretically safe from N95, as long as the seal between the airflow and the face remains secure, can provide effective protection. Those properties have historically been used during periods of supply intervention and/or exceptional use such as outbreaks of airborne diseases by N95 extended use and reuse protocols.

Extended use requires continued use for up to several hours, usually if the risk of disease transmission is small or irrelevant. For several consecutive experiences, the reuse requires removing and dressing the respirator, with or without respiratory decontamination in between.

Nor do they mandate manufacturers to integrate disinfection instructions into the labelling for single-use N95, nor do the CDC guidelines provide instructions for single-course decontamination of the N95 respirators. In bench studies by NIOSH and other organisations, however, a range of proposed methods for N95 single-use disinfection have been assessed. Three broad categories of these methods:

  • Moist heat with autoclaves, pressure cookers, or steam bags with a microwave. A minimum of 10 minutes at 121° C is required to be successful for steam sterilisation. Steam is commonly available in porous materials as N95 filters and not poisonous and completely penetrant, but could harm the filter's polymer fibres and compromise its efficiency.
  • Chemical cleaners, then rinse and dry, applied by soaking or washing. There are several alternatives available, but due to its toxicity and chemical incompatibility with filter materials, this should be determined individually. Depending on the pathogen, minimum concentrations and time can also differ. 
  • UVGI lamps from 200 to 400 nm. The dose needed usually ranges from 10 to 100 mW / cm2, but varies depending on the pathogen, surface form, mode of exposure, and ambient humidity. In a multi-layered N95 filter, penetration may be incomplete. UVGI does not leave a toxic residue but allows spaced or covered enclosed devices to protect users against UV exposure. The use of UVGI equipment is typically costly and can be a big obstacle to use in times of crisis.

Risks Involved with Extended Use of N95 

While extended use and re-use can contribute to N95 conservation in shortages, these practises entail considerable risks and inconveniences, including:

  • Discomfort
  • Bad fitting
  • Lack of filtration efficiency 

Often people ask about using a broken mask again, but it is recommended not to use broken because it can affect your skin and fail to serve the purpose of wearing it. 

Administrative and engineering controls should also be considered to reduce the need to N95s. Management checks are all procedures designed to reduce the N95 requirement by reducing the amount of breathing experiences required. The improvements include hospital visitors' limitation, the use of telemedicine, patient cohorting, and early disease discharge. Technical challenges to airborne pathogens like airflow controls and air purification devices are engineering controls.

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