Masonry heaters produce heat both by radiation and passive convection. Once fired the mass of the heater will emit a constant level of heat for up to 8 hours. The heat is gently convected and radiated from the masonry to the floors, walls, ceiling and the furniture, resulting in high surface temperatures and cool air temperatures. In comparison, conventional heating systems heat the air rather than the surfaces. It is advantageous if the air we breathe is cooler than the furniture we sit on and the floors we walk on.
Because the exterior masonry never becomes hot, only warm, there is no scorching of dust particles, enhancing the chance of respiratory irritation. Furthermore, as masonry heaters heat by gentle convection and radiation, no aggressive conventional air currents are produced to circulate dust and fungal spores, which even unscorched, can contribute to respiratory ailments. Finally, imbalance of the air ionisation caused in part by hot dry heating systems is suspected as promoting ailments of the circulatory system. Due to the subtle way in which masonry heaters give off their heat, they only minimally disturb the balance of ions in the home atmosphere.