Control of the bed thermal environment by a ventilated mattress

human subject response

Abstract

Bioeffluents emitted from person lying down in bed can be removed by ventilated mattress (VM) before mixing with the room air. VM is designed to suck air through an exhaust opening located near the feet and move the sucked air inside the mattress. The air moves through the whole mattress and is removed to the exhaust or cleaned and discharged back to the room. The VM can change the thermal conditions in the bed micro-environment and provide uncomfortable local cooling of the person in the bed. Therefore, the design of the ventilated mattress is further improved by incorporating local heating. The response of people to the bed thermal environment generated by the mattress was studied at three room air temperatures – 19°C, 23°C and 28°C. 30 human subjects (15 males, 15 females) of age 20 - 29 years old and body mass index in the range 18 - 27 were exposed to the bed thermal environment provided by the VM. The subjects were covered with a thin duvet (2.9 clo) at room temperature 19°C, a double cotton sheet at 23°C and a single cotton sheet was used at 28°C. The subjects were dressed with pajama (short-sleeve shirt, shorts) and underwear. Thermal sensation assessment was collected through standardized questionnaires. The subjects answered questions regarding their whole body thermal sensation and local thermal sensation of separate body parts including face, head, neck, chest, back, arms, hands, thighs, lower legs, and feet. The bed thermal micro-environment was adjusted by the exhaust flow rate through the ventilated mattress and the localized heating depending on the acceptability of the subjects’ thermal sensation collected every 7 minutes. The results show that the applied control of the bed thermal environment increased the acceptability of the whole body thermal sensation votes and the risk of local cold discomfort (especially on the feet and hands) decreased over time. Local heating at the feet will be needed to achieve thermal comfort in room temperatures below 23°C. Local heating incorporated in the VM or separate and the airflow through the mattress can be controlled based on physiological signals of the person’s body.