Abstract
A fire detector is the most important component in a fire alarm system. Herein, we present the feasibility of a highly sensitive and rapid response gas sensor based on metal oxides as a high performance fire detector. The glancing angle deposition (GLAD) technique is used to make the highly porous structure such as nanocolumns (NCs) of various metal oxides for enhancing the gas-sensing performance. To measure the fire detection, the interface circuitry for our sensors (NiO, SnO2, WO3 and In2O3 NCs) is designed. When all the sensors with various metal-oxide NCs are exposed to fire environment, they entirely react with the target gases emitted from Poly(vinyl chlorides) (PVC) decomposed at high temperature. Before the emission of smoke from the PVC (a hot-plate temperature of 200 °C), the resistances of the metal-oxide NCs are abruptly changed and SnO2 NCs show the highest response of 2.1. However, a commercial smoke detector did not inform any warning. Interestingly, although the NiO NCs are a p-type semiconductor, they show the highest response of 577.1 after the emission of smoke from the PVC (a hot-plate temperature of 350 °C). The response time of SnO2 NCs is much faster than that of a commercial smoke detector at the hot-plate temperature of 350 °C. In addition, we investigated the selectivity of our sensors by analyzing the responses of all sensors. Our results show the high potential of a gas sensor based on metal-oxide NCs for early fire detection.
Highlights
A fire alarm system is a device to sense one or more products or phenomena resulting from fire and to immediately warn people through visual and audio appliances [1,2]
The module contains analog signal conditioning circuitry which is composed of four different gas sensors, their potentiometric circuits, a 12-bit analog-to-digital converter (ADC), aofmicrocontroller and contains analog signal conditioning circuitry which is composed four different unit gas (MCU)
Ordered metal-oxide NCs were fabricated using a facile and effective method based on glancing angle deposition (GLAD)
Summary
A fire alarm system is a device to sense one or more products or phenomena resulting from fire and to immediately warn people through visual and audio appliances [1,2]. Among the thermal decomposition products of PVC, HCl, CO and VOCs are the major toxicants as sensory and pulmonary irritants which cause respiratory difficulties or death in the case of inhalation for a long time [10,11] Since these gases begin to be gradually released at relatively low temperatures below 200 ◦ C, it is possible to extinguish the fire and escape from the fire by detecting HCl, CO, and VOCs in the initial fire stage. The gas-sensing mechanism of the chemoresistive gas sensor is based on electrical properties, including the resistance, current or voltage change of the sensing layer They are induced from the adsorption and desorption of the gases when specific gases interact with its surface, which is affected by three basic factors, namely the transducer function, utility factor, and receptor function [17,18,19]. At the further elevated temperature of 350 ◦ C, NiO NCs showed the highest response compared with other metal-oxide NCs
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