The plastic housing is very cheap. Two DHT11 sensors are used in my test to a temperature deviation of 4 ° C of each other. If safe to use it on, who wants it more accurately invested 3 euros more per sensor and buys the DHT22 (deviation less than 1 ° C). Connection via 1-Wire, the Arduino with the DHT Library and a 10k resistor. Multiple sensors can be made simultaneously.