The present invention ambient atmosphere monitoring apparatus comprises a gas supplement mechanism, a gas gathering mechanism, a gas back-flow mechanism and a gas monitoring mechanism. The gas supplement mechanism outputting air and CO2, the CO2 is used to mix with the outside air to generate a simulation gas which imitating human exhaled and inhaled gas； the gas gathering mechanism comprising a gathering space to communicate with outside and connects with gas supplement mechanism to generate an object gas； the gas back-flow connects between the gas supplement mechanism and the gas gathering mechanism； the gas monitoring mechanism, being assembled in the gas back-flow mechanism, comprising a monitoring device to monitor the object gas and an electronic device connects with the monitoring device electronically. Wherein, the monitoring device monitors the proportion of CO2 in object gas to generate a gas value, the gas value is received and recorded by electronic device. The present invention imitates human exhale and inhale to monitor the air circulation and confirm the security of laying environment.本發明環境空氣檢測設備包含一氣體供應機構，輸出空氣及二氧化碳，該二氧化碳用以與外部空氣混合形成仿造人體呼吸的模擬氣體；一氣體蒐集機構，具有蒐集空間與外部環境連通，並組裝氣體供應機構來形成目標氣體；一氣體回流機構，組接於氣體供應機構與氣體蒐集機構之間；一氣體偵測機構，安裝於氣體回流機構，具有一偵測該目標氣體的檢測裝置及一電性連接於檢測裝置的電子裝置；其中，檢測裝置偵測目標氣體的二氧化碳比例形成濃度數值，濃度數值由電子裝置取得並記錄。藉此模擬人體呼吸來檢測躺臥環境的空氣流通性，並確認躺臥環境的安全性。
