Design of a fire fighter's protective mask with a thin layer of water

A firefighter's protective mask with a viewing porthole, in which a thin layer of water is used as an optical filter, has been considered in this study. Such mask's structure is designed to solve the task of protecting the firefighter's face from intense thermal radiation in a fire zone. The porthole of the mask is two parallel transparent plates with a gap between them, through which water continuously flows. The porthole exploits the unique optical properties of water, which is transparent in the visible region of the spectrum and opaque in the infrared region, characteristic of fire radiation. In addition to the function of weakening the radiant heat flux, water also performs the function of cooling the protective mask. This paper reports a theoretical analysis of physical processes, the calculation formulae, as well as the estimated calculations of the design and operational parameters for a protective mask under typical operating conditions in a fire zone. In particular, a methodology was devised for calculating water consumption, changes in its temperature, and attenuation of radiant heat flux under given conditions in a fire zone. For example, for a heat flux intensity of 25 kW/m2, a temperature at the fire site of 1200 K, and a water layer thickness in the porthole of 1 mm, a 15-fold attenuation of the heat flux was established. Under these conditions, the maximum operating time in a fire zone reaches 12 minutes, which is three times higher than the similar parameter for existing samples of heat-resistant suits. These parameters indicate the possibility of significant improvement of protective masks for firefighters. Subject to experimental confirmation, the results of this work could be practically applied at design institutions engaged in the development of protective fire-fighting equipment.