The effects of two kinds of mask (with or without exhaust valve) on clothing microclimates inside the mask in participants wearing protective clothing for spraying pesticides

Abstract

We discussed these findings from the viewpoint that the dry and wet heat loss was accelerated through the nose under the influence of a reduced level of clothing microclimate inside mask B, having probably helped selective brain cooling by cooling more effectively the vein circulating blood through the nose.

Effects of wearing N95 and surgical facemasks on heart rate, thermal stress and subjective sensations

“…As mask microclimate temperature is a key parameter indicating thermal stress, we used this parameter to estimate the sample size. According to previous reports, the difference in microclimate temperature between masks is approximately 0.9°C and standard deviation is around 0.5°C (Hayashi and Tokura 2004). From this assumption, a sample size calculation reveals that ten participants are enough to reach an error of probability of <5% and a power of 90%.…”

“…In the World Health Organization (WHO) (2003) and the US Centers for Disease Control (CDC) (2004) guidelines for PPE, facemasks with 95% filtration efficiency or above are required for healthcare workers exposed to SARS patients. Hayashi and Tokura (2004) found that it was important to prevent an excessive increase of microclimate temperature and humidity inside the facemask in order to reduce heat stress on the body when farmers were spraying pesticides in a warm environment. Farquharson and Baguley (2003) reported that Emergency Department (ED) staff taking care of SARS patients at a hospital in Toronto wore double isolation gowns, a hair cap, an N95 facemask, a face shield and two pairs of gloves.…”

Evaluation on Masks with Exhaust Valves and with Exhaust Holes fromPhysiological and Subjective Responses

“…Nielsen et al (1987) has shown that whole body thermal sensation was significantly influenced by the mask air temperature. Further, Hayashi and Tokura (2004) found that the rectal and tympanic temperatures increased more slowly wearing the mask with exhaust valves as compared to those without exhaust valves for most subjects. However, none has provided direct scientific evidence to demonstrate that the microclimate temperature and humidity inside the mask significantly influence whole body thermoregulatory responses.…”

“…The failure to wear them may be due to various sensations of discomfort, many studies having shown a variety of physiological effects associated with their use. In general, the research has shown changes associated with increased effort of resistance to breathing due to increased dead air space, increased thermal stress and a variety of cardiovascular stresses (Harper et al, 1989;White et al, 1991;Nielsen et al, 1987;Jones, 1991;Hayashi and Tokura, 2004). According to Nielsen et al (1987), the acceptability of both the ambient thermal environment and of the thermal microclimate in the masks was primarily determined by the ambient air temperature, but it was influenced also by the clothing microclimate temperature and humidity inside the mask.…”

“…Also, subjective ratings of humidity, hotness, breath resistance, and overall discomfort increased gradually with the duration of exercise and the workload . Hayashi and Tokura (2004) found that, in order to reduce heat stress of the body when the farmers were spraying pesticide in a warm environment, it was important to prevent an excessive increase of microclimate temperature and humidity inside the mask. They found that a mask with an exhaust valve was effective in reducing temperature and humidity inside the mask when two kinds of mask (with and without exhaust valve) were compared.…”