🌼【Exclusive CO Peak Recording Graph】Logs hourly CO levels for the past 8 hours to help you spot hidden spikes and take early action for indoor air safety. 🌼【Customizable CO alert threshold】Set your preferred trigger (10–200 ppm) for bedrooms, RVs, tents, or workshops; screen color changes reflect elevated levels fast. 🌼【Japan-made electrochemical CO sensor (0–1000 ppm) 】Plus ambient temperature (-40–257 °F) and humidity (0–100 %RH) provide accurate, trusted readings for safer indoor air. 🌼【Multi-mode alerts】Choose visual (screen color change), LED, or loud audible reminder (up to ~85 dB) with power-saving or always-on display modes for flexible use. 🌼【Compact & rechargeable 】USB-C 2000 mAh battery (~60 h power-saving) with included stand, lanyard and adhesive. Pocket-sized convenience (0.79″×2.21″×3.52″), ideal for home, travel, RV. 🌼【Long-lasting design】Built with premium components for a service life of up to 7 years, delivering reliable monitoring and better value over time. 🌼【How to Test It】 To confirm the device is working, expose it to smoke from a cigarette or burning paper—the CO reading should rise quickly. Do not use car exhaust or test in open, windy areas, as CO levels may be too low to detect. If there is no carbon monoxide present, the display will correctly show 0 ppm. 📟【Shopping Confidence】Your satisfaction is our priority. This CO monitoring meter uses high-precision, stable, and sensitive sensors with a clear HD display and long-lasting rechargeable battery. We provide lifetime technical support and a 24-hour response through Amazon Customer Service—so you can shop with confidence. Meet your pocket-sized air safety companion. This 3-in-1 CO Monitoring Meter blends a precision Japan-made electrochemical sensor with temperature and humidity tracking to give a clear picture of your indoor air. Watch the exclusive Peak Recording Graph to catch hourly CO trends over the last 8 hours—knowledge that helps you act timely. Program your own alert threshold (10–200 ppm) for personalized safety, while the color-changing display, LED, and up to ~85 dB audible reminder keep you instantly informed. The USB-C 2000 mAh rechargeable battery lasts ~60 hours in power-saving mode. Includes handy stand, lanyard, and adhesive—compact, portable, and designed for use anywhere from bedrooms to RVs to tents. Not a substitute for fixed alarms—intended for portable indoor air awareness.