Design, construction and validation of a simple, low-cost phi meter

Abstract

The best correlation between the yields of the major toxicants in fire smoke and the fire condition is obtained by expressing the ventilation in terms of the equivalence ratio, phi. Phi meters allow this fuel-air equivalence ratio to be determined during a large-scale fire test. The original design used a platinum catalyst, a large furnace, and required pure oxygen. This work aimed to make a simple, low-cost device which could monitor the equivalence ratio during a large-scale fire test. The current design produces the same quality of measurement with a much smaller footprint and throughput. Benefits include enhanced portability, reduction in sample gas cleaning and drying requirements and lower cost. The work showed that normal furnace components (alumina and silica) provide suitably catalytic surfaces at 900 °C eliminating the requirement for platinum catalysts and the use of pure oxygen. The ISO/TS 19700 steady state tube furnace (SSTF) was used to validate the phi meter measurements as it can both pre-set and independently quantify the equivalence ratio during a test. Long sample collection times were overcome with a larger sampling pump and effluent being split between the phi meter furnace and the exhaust. It is hoped that this simpler, optimized apparatus will encourage more widespread use and lead to better prediction of smoke toxicity.