Study on the kinetic characteristics of trace harmful gases for a two-person-30-day integrated CELSS test.

Abstract

A two-person-30-day controlled ecological life support system (CELSS) integrated test was carried out, and more than 30 kinds of trace harmful gases including formaldehyde, benzene, and ammonia were measured and analyzed dynamically. The results showed that the kinds and quantities of the trace harmful gases presented a continuously fluctuating state during the experimental period, but none of them exceed the spacecraft maximum allowable concentration (SMAC). The results of the Pre-Test (with two persons without plants for 3 days) and the Test (with two persons and four kinds of plants for 30 days) showed that there are some notable differences for the compositions of the trace harmful gases; the volatile organic compounds (VOCs) such as toluene, hexane, and acetamide were searched out in the Pre-Test, but were not found in the Test. Moreover, the concentrations of the trace harmful gases such as acetic benzene, formaldehyde, and ammonia decreased greatly in the Test more than those in the Pre-Test, which means that the plants can purify these gases efficiently. In addition, the VOCs such as carbon monoxide, cyclopentane, and dichloroethylene were checked out in the Test but none in the Pre-Test, which indicates that these materials might be from the crew's metabolites or those devices in the platform. Additionally, the ethylene released specially by plants accumulated in the later period and its concentration reached nearly ten times of 0.05 mg m(-3) (maximum allowed concentration for plant growth, which must have promoted the later withering of plants). We hoped that the work can play a referring function for controlling VOCs effectively so that future more CELSS integrating tests can be implemented smoothly with more crew, longer period, and higher closure.