Edge-Enabled Ambient Condition Surveillance with Firmware-Resident Health Classification and Thingspeak Telemetry on ESP32

Abstract

Most people spend the majority of their time indoors, yet very few indoor spaces give occupants any real-time indication of whether the air they are breathing is actually safe. Temperature creep, rising humidity, and slowly deteriorating air quality tend to go unnoticed until discomfort sets in — by which point conditions may already be affecting health and concentration. This paper describes a low-cost sensing node designed to address that everyday blind spot. Built around an ESP32 microcontroller interfaced with a DHT11 temperature-humidity sensor and an MQ-135 gas sensor, the system continuously tracks ambient temperature, relative humidity, and air quality, uploading each reading to a ThingSpeak cloud channel every 15 seconds over the ESP32's built-in Wi-Fi radio. What makes the design distinct is that environmental interpretation happens on the device itself: a rule-based advisory classifier embedded directly in the firmware evaluates every measurement against predefined thresholds and immediately outputs a health status — Normal, High, or Good — without depending on cloud connectivity to reach a decision. During field testing, the node operated without a single failed transmission across the full observation window, recording temperatures between 32.6°C and 33.1°C, relative humidity between 40.5% and 42.0%, and air quality readings ranging from 300 to 658 ADC counts, all correctly classified in real time. The result is a practical, affordable system that puts environmental awareness and cloud-based data logging together on a single board, making continuous indoor monitoring genuinely accessible without specialized infrastructure.