Physiological assessment of the passive children's hood.

The physiological effect of the "passive children's hood" (PCH) was studied in 24 children: 8 toddlers (3-4.5 years old), 8 pre-school pupils (4.5-6 years) and 8 first- and second-grade pupils (6-8 years). This device consists of a children's gas mask and a transparent PVC (polyvinyl chloride plastic) covering (hood). Inspiratory CO2 and O2 (FiCO2 and FiO2, respectively), temperature and humidity were monitored at 10-min intervals while the children were occupied with sedentary activities (playing and watching TV) in a sealed room. Ambient temperature and relative humidity were approximately 27 degrees C and 75% respectively. In the PCH space the temperature was 2 degrees C higher and humidity was near saturation at the end of exposure. FiCO2 in 12 children exceeded 2%, which is the upper acceptable limit according to industrial standards. In four of them FiCO2 was greater than 4% and FiO2 less than 16%. Twenty-two children tolerated the PCH for 92 +/- 35 min (range 24-133 min) with no physiological complications. A significant correlation was found between childrens' age and tolerance time (r = 0.47, P less than 0.025). We conclude that children whose masks are not well adjusted may be exposed to rebreathing CO2-enriched air.