Journal of Biosciences and Medicines, 2014, 2, 1-5
Published Online June 2014 in SciRes. http://www.scirp.org/journal/jbm
How to cite this paper: Zhu, J.H., et al. (2014) Evaluation of Nasal Functions While Wearing N95 Respirator and Surgical
Facemask. Journal of Biosciences and Medicines, 2, 1-5. http://dx.doi.org/10.4236/jbm.2014.24001
Evaluation of Nasal Functions While
Wearing N95 Respirator and Surgical
Jianhua Zhu1*, Shujin Lee2, Deyun Wang3, Heow Pueh Lee1,4
1Department of Mechanical Engineering, National University of Singapore, Singapore Cit y, Singapore
2Department of Surgery, National University Health System, Singapore City, Singapore
3Department of Otolaryngology, National University of Singapore, Singapore City, Singapore
4National University of Singapore (Suzhou) Research Institute, Suzhou, China
Received February 2014
There is a lack of reported studies on how the long duration wearing of N95 respirators or surgical
facemasks will affect the upper airway functions. Considering the frequency of mask wearing es-
pecially in hospitals and during an outbreak of influenza, it is essential to have such data docu-
mented. Therefore, the current study is to establish the effect of long duration wearing of N95 and
surgical facemasks on upper airway functions. 47 staffs of National University Hospital Singapore
in 2013 were recruited. Each of the volunteers wore both N95 respirator and surgical facemask for
3 hours on two different days. During the period of mask wearing, relative airflow rates were rec-
orded. Smell function test was carried out before and after mask wearing. The results show that no
significant change of smell test score was found after removal of both the two types of masks. With
N95 respirator, more air was breathed into the upper airways compared to surgical facemask.
N95 Respirator, Surgical Facemask, Smell Function Test, Spiromet ry
Facemasks are important components of personal protective equipment for medical personnel and workers in
atmospherically-hostile environment. This is especially true for healthcare workers who need to interact with
patients inflicted by airborne transmitted diseases such as the Severe Acute Respiratory Syndrome (SARS) out-
break that occurred in March 2003 . Patients are also advised to put on facemasks in public areas to prevent
the spread of airborne infectious diseases. Many national and international health agencies recommended the use
of facemasks for the recent influenza A (H1N1) pandemic .
Many reported studies were done on the effectiveness of various facemasks in filtering out airborne pathogens,
but very few of them focused on the discomfort level of their use. There were reported studies on the effects of
J. H. Zhu et al.
wearing N95 facemask and surgical facemasks on thermal stress and subjective sensations of the wearer .
Healthcare workers have to wear the facemasks for up to 12 hours and this may induce physiological stress on
them . In another reported study by Lim et al. , out of 212 healthcare workers who participated in the sur-
vey, 37.3% reported headaches when they wore the facemasks. Farmers wearing facemask while spraying pesti-
cides in warm environment were also reported to experience heat stress on the body due to increased tempera-
ture and humidity within the facemask . Although comfort level is subjective, there are a few parameters
which can be used to correlate this comfort level. For example, a drier and cooler micro-climate leads to better
comfort . A higher expiratory and inspirational resistance reduces the ease of breathing and thus causes dis-
comfort. A lower air flow volume means that the wearer may need to breathe in harder to get the same amount
of fresh air required. In a recent study by Roberge et al.  using an automatic and metabolic simulator as a
human surrogate, inhalation and exhalation resistances were found to increase by 0.43 and 0.23 mm of H2O
pressure and it was concluded that increased exhaled moisture due to the wearing of facemask would not add
significantly to the breathing resistance. However, the findings on surrogate were contrary to the common per-
There is a lack of reported studies on how the long duration wearing of N95 respirators or surgical facemasks
will affect the upper airway functions. The current study, therefore, is aimed to evaluate the effects of long dur-
ing wearing of N95 respirators and surgical facemasks on upper airway functions such as smell function and air-
Each of the participants would attend two experimental sessions. In the first session ( S1 ), participants were re-
quested to wear a N95 respirator (3MTM 8210) for 3 hours, while in the second sessio n (S2) , participants were
requested to wear a 3-ply surgical facemask (3MTM earloop mask 1826). There are 63 participants involved in
the first phase of this project, of which 5 participants were not qualified due to nasal diseases such as nasal polyp
and rhinitis, 6 participants did not co mplete both of the 2 sessions and 5 other participants did not show up on
the scheduled experimental date. 47 data sets were successfully collected, with 6 male subjects and 41 female
subje c ts .
In the first 30 minutes of the two sessions, the participants were informed with details of the experiments,
signed the consent form, and adapted to the room environment. Smell identification test was also done during
this period as baseline of smell function. At the end of the first stage , the participants were told to put on the
sensor of spirometry around the nostrils to measure the nasal airflow rate. In stage 2 (30 min to 3 hours 30 min),
the participants were told to put on either N95 respirator (first session) or surgical facema sk (second session).
Within this period, the airflow rates through nostrils were monitored. At the time of 3 hours 30 minutes, the
masks were removed, and smell identification test was carried out again once the masks were remov ed. The
RHINO-SYS (Happersberger otopront GmbH) was used to carry out the spirometry test. The smell identifica-
tion test (Sensonics, Inc.) was used to measure the smell functions of the participants. In addition, the smell test
was carried out only on the first 20 subjects and rescinded for the latter subjects, since no significant difference
was found in the smell test scores between the results measured before and after wearing the masks.
3.1. Airflow Rate
The Rhino-Move of Rhino-Sys (Happersberger otopront GmbH) is a spirometer measuring the relative airflow
rate passing through the nostrils during respiration. The relative airflow rate is obtained by recording the kinetic
pressure fluctuations during respiration . By extracting the recorded relative airflow rates at certain time
points (every 15 min) and averaging the airflow rates at these points among all the 47 subjects, the mean airflow
rates at these points while wearing the masks are calculated. Figure 1 shows the averaged airflow rate of left
and right airways at the 16 time points. In session S1, the airflow rate was generally larger in the right nasal air-
way in the first 2 hours compared to in the left nasal airway. In the last 1 hour of wearing N95 respirator, the air-
flow rates became comparable between the two airways. While during session S2, the airflow rate was compa-
rable between the two airways through the whole 3 hours period. When adding up the airflow rates in the left
and right airways, as shown in Figure 2, the relative respiratory airflow rates in nasal cavities during session S1
was generally larger than during session S2.
J. H. Zhu et al.
Figure 1. Averaged airflow rates during the 3 hours mask
wearing period in sessions S1 and S2 through left and right
Figure 2. Averaged airflow rates during the 3 hours mask
wearing period in sessions S1 and S2 through the whole nas-
By integrating the airflow rate with time during the 3 hours, the relative respired air volume is calculated with
the equation below:
where V is the mean relative respired volume among the 47 subjects, vl and vr are the airflow rates through the
left and the right nostrils, respectively. The volumes of inspired air and expired air in one respiratory cycle are
assumed to be equal. As shown in Figure 3, the mean volume of relative respired air during the 3 hours period is
significantly larger in session S1 (2866.42 L) than in session S2 (2328.96 L).
3.2. Smell Function
Smell function test was done on 20 subjects before and after wearing the two types of masks in sessions S1 and
S2. As shown in Table 1, the averaged score of smell identification test does not change much after wearing
masks for 3 hours in both S1 and S2.
J. H. Zhu et al.
Figure 3. Averaged volume of air breathed into the
nasal cavity during the 3 hours mask wearing period in
sessions S1 and S2.
Table 1. Averaged score of smell identification test before and after wearing
of the masks in sessions S1 and S2.
Averaged Score Pre*
33.25 (±2.92) 33.45 (±2.96)
Averaged Score Post 33.20 (±2.76) 33.10 (±3.41)
*full mark: 40.
The subjective ratings for perceptions on odorous while wearing the masks, reported by Li et al. , indicates
that the smell functions might be different while the subjects wearing different types of masks. However, in the
current study based upon objective smell identification test, no significant effect of wearing both N95 respirator
and surgical facemask on nasal smell function was found. Since the averaged scores of smell function test are
similar between the results measured for N95 respirator and surgical facemask, long-duration of mask wearing
itself would not affect nasal smell function.
The chance for the particles such as bacteria penetrating the masks increases with airflow rate . According
to the present results, the relative airflow rate during respiration with masks on is significantly higher for N95
respirator compared to surgical facemask. However, since the N95 respirator is much more effective in filtering
external particles than surgical facemask, the respirator is still a better choice.
Long-duration wearing of N95 respirator induced more air into the upper airways compared to surgical face-
mask. No significant effect of long duration wearing of both N95 respirator and surgical facemask was found on
The authors would like to acknowledge the support by the Academic Research Grant (CDPHRG/12NOV001)
from the Ministry of Health, Singapore. This research has been approved by the relevant Institutional Review
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