use zmod4410 to estimate formaldehyde concentration

Question

Hi, 
 It's confused when read below words from document: 
 
 Does that mean I can use tvoc value from zmod4410 to estimate formaldehyde concentration roughly? 
 If not how I can know the zmod4410 can detect formaldehyde concentrations down to 50ppb? 
 Thanks!

JE_REN · Answer

Hi Stanley, 
 The MOx material will always react to all present VOCs. Therefore we call it Total VOC (TVOC) sensor. Although the sensor can detect trace gases such as formaldehyde, we don't have selectivity for this gas when present in a gas mixture. There is a possibility for semi-selectivity by changing the operation mode to identify different groups of chemicals gases, but not a single gas. This is the case for the Sulfur Odor algorithm, where Hydrogen Sulfide (H2S) and Dimethyl sulfide (DMS) are classified selectively against Ethanol (C2H5OH).. 
 Thanks JE_REN

JE_REN · Answer

Hi There, The ZMOD4410 will detect all TVOC gases but none of them selective. Formaldehyde is most likely the most tricky VOC because of the necessary low detection limits and a typically lower sensitivity of the sensing element. Also, a reliable formaldehyde measurement is only possible without the presence of any other VOC (e.g. alcohols). Since the ZMOD4410 is calibrated with typical indoor TVOC it will underreport for formaldehyde. The only option would be to develop your own calibration and algorithm using our raw sensor resistance output. BR JE_REN