IoT-Based Integrated Health and Environmental Monitoring System using ESP32 Microcontroller

Monitoring a patient at home loses its value the moment the internet goes down — yet nearly every published system fails silently in exactly that situation. This paper reports a single-board, eight-channel health-and-environment monitor built around an ESP32-WROOM-32 that was designed from the first day to treat network absence as a normal operating condition rather than an error state. Sensors cover optical pulse oximetry and SpO₂ (MAX30105), axillary body temperature (DS18B20), single-lead ECG (AD8232 front-end with a four-stage IIR filter chain), indoor climate (DHT11), combustible gas (MQ-2), ambient light (LDR), and GPS position tagging (NEO-6M). A Blynk mobile dashboard streams readings when Wi-Fi is present; when it is not, the SSD1306 OLED and piezo buzzer continue without any change in behaviour. Bench evaluation produced: heart-rate mean error 2.3 bpm (n = 5, σ = 1.8 bpm); SpO₂ within 1.8 percentage points of a hospital reference; body temperature within 0.2 °C of a calibrated clinical probe; gas-alarm latency under 500 ms on every trial; 95 of 100 simulated network cuts recovered within 5 s; and 72 hours of unattended operation with zero failures.