Subsystem was developed for breathing metabolic simulator which adjusts temperature and humidity of air to levels of human exhaled breath. Temperature-humidity subsystem is described, consisting of aluminum enclosure with 400 watt heat sheet glued to bottom, vertical separators, inlet connection, and check valve

Bartlett, R. G.

Hendricks, C. M.

English

NASA Technical Reports Server

December 1972	 B72-10660 
NASA TECH BRIEF 
NASA Headquarters 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Temperature and Humidity Control 
of Simulated Human Breath 
.
The problem: 
Simulation of the exhaled human breath is provided by 
the recently developed breathing metabolic simulator (see 
Notes). The exhaled breath which the simulator provides 
must be identical in temperature and humidity to that of 
a human who is subjected to conditions ranging from rest 
to hard work. 
The solution: 
A subsystem was developed for the breathing meta-
bolic simulator which adjusts the temperature and humid-
ity of air to levels of human exhaled breath. 
How it's done: 
The temperature-humidity subsystem is shown in the 
figure. It consists of an aluminum enclosure with a 
400-watt heat sheet glued to the bottom. Vertical 
Dry Bulb ______ 
Thermistor	
• ' Outflow
Heater Thermistor 
Wet Bulb 
Thermistor
separators (perforated metal) are fastened to the sides at 
the heater ends and separate the chamber into three areas. 
The main area is filled with a 10-by-20-cm (4-by-8-inch) 
gauze surgical sponge which sits in water covering the 
heater and acts as the moisture transfer media by wicking 
action. 
The inlet end of the chamber contains an inlet 
connection and check valve and is topped by a sealed 
reservoir of approximately half liter (one pint) capacity. 
Water level is maintained in the chamber at the bottom 
III	 I 
II	 I	 I
10-by-20 cm (4 by 8 Inches) 
Gauze Surgical Sponge
Laid Horizontally
From End To End Of
Heater
Inflow 
I	 I	 I
Heat Sheet (40N) 
.-
(continued overleaf) 
	
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level of a tube. This tube connects the chamber to the top 
of the reservoir. The reservoir also has a shorter outlet 
with a check valve. (Relative air pressure is maintained in 
the reservoir to control water release). 
The outlet end of the chamber contains both wet and 
dry bulb thermistors, used for monitoring exhaled humid-
ity, and an outlet connection with check valve. 
In operation the heater, when energii 'ed remotely, is 
controlled by a thermistor located in the outlet connec-
tion to maintain outlet temperature at 37±1°C 
(98.6±2 0F). Relative humidity is maintained by the 
chamber configuration requiring airflow through the 
surgical sponge. The chamber has been sized such that, 
even under the largest simulated breath volume, the 
complete breath volume will be retained in the chamber 
for one complete breath cycle.
Notes: 
1. Additional information is contained in the following 
Tech Briefs: B72-10657 (HQN . 10766), B72.10658 
(HQN-10776), B72 . 10659 (HQN-10777), and 
B72-10661 (HQN-10779). 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Headquarters 
Code KT 
Washington, D. C. 20546 
Reference: B72-10660 
Patent status: 
NASA has decided not to apply for a patent. 
Source: R. G. Bartlett and 
C. M. Hendricks of
IBM Corp.
under contract to
NASA Headquarters
(HQN-1 0778) 
B72-10660
	 Cat egor4


Temperature and humidity control of simulated human breath

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