When I was updating this page, then coupon price was $20.99 for Smart Tuya Zigbee WIFI Airbox CO2 Formaldehyde VOC Detector (in Banggood). Check coupons or create price alert down below. You probably want to know what is the best price?
Latest coupon and price update (UTC):
Smart Tuya Zigbe WIFI Airbox CO2 Formaldehyde VOC Detector Temperature Humidity Sensor App Control Smart Home Scene Linkage Work with Amazon Google Assistant – Zigbee
Banggood ($20.99)
Banggood warehouse is located in China. Is it good price? Good news! This is great price, coz it’s the lowest in CouponsFromChina database! There is one coupon right now! Check this out.
Link: Banggood product page
Price without coupon: $21.99
1. ($20.99): BG977107
coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for Smart Tuya Zigbee WIFI Airbox CO2 Formaldehyde VOC Detector.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).