Application of a novel formaldehyde sensor with MEMS (Micro Electro Mechanical Systems) in indoor air quality test and improvement in medical spaces

In the indoor air environment in Taiwan, formaldehyde concentration stays at a high level, which is an important issue affecting indoor air quality, and the formaldehyde issue in medical building spaces is more severe. The novel formaldehyde sensor based on microelectromechanical systems (MEMS), which uses quartz glass as basic material, platinum as micro heater resistance, as well as a heat sensing layer and NiO film as a sensing layer. NiO film was used to form a sensing layer in the method of sputter deposition. Platinum was used as electrode to measure and sense resistance change. When there was formaldehyde gas in the environment, the electrical conductivity on the NiO film increased, thus causing the resistance on the sensing layer to decrease. The sensor displayed the value of formaldehyde concentration. The novel formaldehyde sensor with MEMS was applied and tested in a large medical center (medical space) in southern Taiwan. The formaldehyde concentration in 120 points in one medical building was tested. The results showed that the indoor formaldehyde concentration was between 0.01-2.31 ppm, exceeding the indoor air quality standard - 0.08 ppm, and the failure rate of the whole building was over 50%.