Indoor Air Quality in an Auto Repair Shop: A Case Study

: The aim of the paper was to conduct an indoor air quality (IAQ) assessment in an auto repair shop, measuring CO 2 and CO concentrations. Carbon monoxide and carbon dioxide concentrations were measured for a week. Two Testo 435-4 gauges were located at head height of an adult person (ca. 170 cm above the floor) in a room. The CO 2 concentration was measured with an IAQ probe, which measures dew point temperature, psychrometer temperature and absolute pressure in indoor air. The second gauge was connected to a CO probe. Measurements were taken every 5 min and were averaged across an hour. Uncertainties were estimated using square-root combinations of fixed errors and random errors at a 0.05 level of statistical significance. The measurements were conducted from 17 November to 23 November 2018. The following graphs were plotted for carbon dioxide and carbon monoxide: hourly averaged concentration and 8 h averaged concentration. The results were discussed and compared to Polish, foreign and international standards and recommendations. It was found that the auto shop was in danger of negligence according to Polish law as well as nonfulfillment of healthy recommendations. An exhaust extraction system should be installed.


Introduction
Hundreds of people in Europe are killed per year by carbon monoxide. CO is generated by malfunctioning boilers or it infiltrates from garages. In generally, it is a product of incomplete combustion [1]. Moreover, a problem also exists in the garages wherein the concentration CO is not taken into consideration. The CO mole fraction exceedance was measured in a multi-car garage by Gładyszewska-Fiedoruk and Nieciecki [2], which inspired the authors of this paper to investigate this problem in other motorisation areas.
Carbon monoxide binds with haemoglobin to form carboxyhaemoglobin (COHb), which reduces the amount of oxygen supplied by the blood. As a consequence, people suffer from tissue hypoxia at low exposure levels. At higher concentrations, carbon monoxide significantly decreases oxygen consumption by the brain, the heart, exercising skeletal muscle and developing foetuses (cf. Word Health Organization WHO [3]). Non-smokers in certain jobs can have long-term COHb concentrations up to 5%, while COHb content in heavy cigarette smokers can be up to 10%. Nonsmokers, the foetuses of non-smoking pregnant women and people with coronary artery disease should be protected in such way that the COHb level of 2.5% is not exceeded (cf. WHO [3]). This guideline can be met if a certain the CO concentration with respect to time is not exceeded. The comparison among WHO [3], USA [4], German [5] and Polish [6] recommendations is presented in the full text Nieciecki and Gładyszewska-Fiedoruk [7] reported the human body's reactions to particular CO2 concentration values in the air. Below is listed the volume percentages and human organism reactions that may appear in different job conditions, selected from the work of Nieciecki and Gładyszewska-Fiedoruk [7]: • 0.15%-sense of impure air and sense of stuffiness; • 0.2%-weakened individuals that suffer from respiratory diseases may cough or sometimes suffer from syncope; • 1%-breath frequency is increased; • 1.5%-mild metabolic stress appears after a longer time of respiration; this is the maximal tolerated concentration in submarines and space ships.
The volume percentage of 0.15% means 0.0015 m 3 of CO2 or 1.5 dm 3 in 1 m 3 of air. The European Garage Equipment Association (EGEA) warns that harmful exhaust is emitted from even modern combustion engines. It publishes the following general recommendations [8]: • Exposure to vehicle exhaust emissions indoors should be avoided whenever possible; • If safety cannot be guaranteed, the workspace should be equipped with an exhaust extraction system to protect the workers against hazardous substances; • Exhaust emissions should be captured at source, which means directly at the exhaust tailpipe.
The exhaust nozzle or funnel should be designed so that 100% of the exhaust emissions can be captured; • Exhaust extraction systems should work at vacuum gage pressure; • The extraction volume should be at least 25% above the maximum emitted exhaust volume; • The extraction system specification should accommodate the largest engine in use at the workplace.
The EGEA [8] recommends different extraction volume flow rates depending on engine volume and the type of service: Ventilating or air conditioning systems are controlled by the value of indoor temperature or relative humidity. Although carbon dioxide is considered a pollutant and its gains are taken in consideration in air balance, its concentration is not controlled in ventilation systems (cf., e.g., [9]).
Carbon monoxide is much more harmful substance by far. However, there is no set concentration limit of this poisonous substance in ventilation system controllers. The general aim of the paper is to facilitate a change in attitude towards this issue, so that the concentrations carbon oxides, especially carbon monoxide, would be the desired values determined by the controllers of a ventilation system in any place where exhaust fumes are emitted. The particular goal is to convince each auto repair shop owner that ventilation system installation is a necessity.

Materials and Methods
The measurements were conducted in a three-place auto repair shop with a staff of four people. The building is located in a county town in the northeast part of Poland. It was constructed with perforated brick and insulated with Styrofoam. The shop is not ventilated with a stack effect nor with mechanical ventilation. The only form of ventilation is infiltration through the relatively large and unsealed doors. The window frames are made with Polyvinyl chloride (PVC). This one-week experiment is a part of an experiment series that was conducted in different seasons in one location. It was conducted in autumn, November 2018, which was during the heating season. For this reason, the garage door was opened only when a car was being driven in or out. A probe for carbon monoxide concentration measurement and another probe for carbon dioxide content measurement were placed 170 cm above the floor.
The maximum 8 h average was calculated from moving averages, calculated every hour from eight 1 h averages over a 24 h period

The Results
The recommended CO2 level (1000 ppm) was exceeded on 17 November for 3 h (from 11:00 to 13:00) with the maximal value at 2578.1 mg/m 3 . A greater concentration was recorded on 19 November for 2 h (8:00 and 9:00) at the maximal level of 2982.5 mg/m 3 . On 20-23 November, there were sporadically occurring 1 h CO2 exceedances, whose concentration values reached up to 3264.4 mg/m 3 .
In the case of carbon monoxide, the maximal measured value was 480.88 mg/m 3 on 22 November at 9:32. The short-term exposure limit, according to WHO recommendations [3], (100 mg/m 3 per 15 min) was exceeded twice. The first exceedance lasted 50 min on 22 November, between 8:57 and 9:47, with an average value of 212.07 mg/m 3 , the fifteen-minute means changes from 117.45 mg/m 3 to 402.91 mg/m 3 . The second time the limit was exceeded occurred 10 h later, i.e., between 19:22 and 19:42, with an average value of 112.04 mg/m 3 . The Polish regulation was exceeded the first time, coinciding with the first exceedance of the WHO recommendations. In the second case, the exceedance lasted 15 min from 19:27 to 19:42 at 119.02 mg/m 3 .
The 30 min exposure limit (60 mg/m 3 in WHO recommendations [3]) was exceeded six times. There was no exceedance in terms of the time-weighted average CO2 concentration. However, the time-weighted average CO concentration was too high in four consecutive days from 20 to 23 November.

Conclusions
The results of the measurements lead to the conclusion that working in this garage can threaten employees' health. The lack of any ventilation is not acceptable, and results in the nonfulfillment of WHO [3] recommendations on numerous occasions. What is worse, the regulations of the Ministry of Economy and Labour [10] were breached on four constitutive weekdays. Such situations originate from the lack of fulfilment of the guidelines of the European Garage Equipment Association [8].
So as to improve work conditions and save workers from exposure to poisonous carbon monoxide, the installation of an exhaust extraction system that satisfies EGEA indications is recommended.
Author Contributions: A.G. and K.J. conceived and designed the experiments; K.J. performed the experiments; A.G. created the calculation algorithm; K.J. did the computations; A.G. and K.J. analysed the data and wrote the paper.