Abstract
<title>Abstract</title> <p>Domestic and industrial accidents involving gas leaks and fires continue to be significant causes of fatalities worldwide, especially in low- and middle-income countries where affordable safety infrastructure is scarce. Existing commercial alarm systems either lack remote notification capability or rely on internet connectivity, rendering them unusable in areas without broadband access. This paper presents the design, implementation, and experimental evaluation of a low-cost SMS-based remote monitoring and control system for flame and gas leak detection. The system uses an Arduino ATmega328P microcontroller interfaced with a SIM800L GSM/GPRS module and digital flame and gas sensors. A bidirectional SMS communication protocol enables real-time alerts for hazardous events and remote actuation of up to seven relay-controlled output devices. Experimental results demonstrate an average SMS delivery latency of 4.2 s (SD = 1.8 s), 100% alert reliability over 200 test cycles, and a command execution success rate of 98.5% across 300 attempts. Additionally, the system is compared with WiFi-based solutions, demonstrating superiority in scenarios where internet infrastructure is absent or unstable, owing to its use of the 3G/GSM cellular network. The total system cost is approximately R$ 180.00 (USD $ 35), making it an accessible solution for residential and small-scale industrial applications in developing regions.</p>