New units for indoor air quality: decicarbdiox and decitvoc

Two new units are proposed for the evaluation of indoor air quality using the decibel concept, which give a much better approximation of the human perception of odour intensity, compared to the CO2 and total volatile organic compounds (TVOC) concentration scales: the decicarbdiox and the devitvoc. On the psychophysical scale according to Yaglou, the weakest odour that can be detected by the human smell sensors is equal to one, and corresponds to the lower limit of percentage dissatisfaction (PD) of 5.8%. It is equivalent to: (1) a CO2 threshold concentration of 485 ppm-0 dB (odour CO2)-0 dCd (decicarbdiox), and (2) a TVOC threshold concentration of 50 micrograms m-3-0 dB (odour TVOC)-0 dTv (decitvoc). The upper limit is determined by the initial value of toxicity: (1) CO2-15,000 ppm-134 dCd, and (2) TVOC-25,000 g/m-3-135 dTv. Optimal pollutant values (corresponding to PD = 20%) and admissible values (PD = 30%) for unadapted and adapted persons are calculated. Long-term tolerable values (determining the sick building syndrome range) and short-term tolerable values (the beginning of the toxic range) are also stated. The same system used to evaluate noise can be used to evaluate air quality. Additionally, the contribution of the individual constituents (at present acoustic and odour) to the overall quality of the environment can be ascertained. The new units dCd and dTv can express an increase or decrease in air contamination, e.g. by the use of air cleaners, new building materials etc. The proposed system of using dCd and dTv is compatible with BSR/ASHRAE 62-1989 R which can be used to determine the required volume of fresh air for ventilation by an improved method, which takes into account different levels of required indoor air quality.