Minimum Permissible Outdoor Air Flow Rate for Removing Substances from the Room Considering the Effect of the Harmful Action Summation


Annotation:

For the first time it was proposed when assessing safety of the air environment by the sum of relative concentrations of the harmful substances with the effect of summation of action, to consider not only the substances emitted in the room, but also other substances entering the room only with the supply air.
To calculate minimum allowable intake air flow rate L, which ensures safety of the substances with the summation of the action, the formula is proposed, which is obtained by jointly solving the air safety conditions, and the dependences of the concentrations of harmful substances in the working area on the air flow rate, its contamination, and other factors.
The example of an illustrative calculation of the minimum allowable intake air flow rate for three substances with a summation of the harmful effect is given. Of these, the first two substances are released in the room and come with the supply air, and the third substance enters the room only with the supply air.
It is shown that when the air flow rate is found, the sum of the relative concentrations of three substances in the room is equal to one, that is, the safety condition is met at the limit. At the same time considering the substance in the supply air, which was not released in the room, required (in the example considered) an increase in the air consumption L by 20 %.
Similar calculations L were performed based on the method of SP 60.13330.2020, according to which, when several harmful substances with the effect of summation of action are released in the room, the air exchange L should be determined by the sum of the air consumption Lв calculated for each substance. It was established that the expenses found by this method turned out to be 20–30 % less safe, therefore, they are not correct and do not ensure safety.
The new method for calculating L, described in the article, is proposed to be considered in the regulatory documents.

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DOI: 10.24000/0409-2961-2021-12-44-50
Year: 2021
Issue num: December
Keywords : ventilation harmful substance efficiency of substance removal effect of summation of action safety condition minimum permissible air exchange
Authors: