• Journal of the Korean Society of Safety
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• v.27 no.1
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• pp.1-6
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• 2012

In crowded subway stations indoor air quality (IAQ) is a key factor for ensuring the safety and health of passengers. Since physical variables that describing IAQ such as the concentration of particulate, $CO_2$, VOCs and biological agents need to be closely monitored and controlled in multiple locations within subway stations and in remote sites, concept of web-based monitoring and control network using both wireless and wired media needs to be implemented. Connecting remote wireless sensor network and device (LonWorks) networks to the IP network based on the concept of VDN can provide a powerful, integrated, distributed monitoring and control performance. In this study, performance of wireless and wired network in VDN for monitoring and control of IAQ in subway stations is evaluated. Specifically, delay induced in wireless and wired networks, and data transmission rate are evaluated. A key parameter is identified in assuring safety and health of passengers in subway stations.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.793-801
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• 2004

A passive sampler has been developed for measuring formaldehyde in air using methyl yellow and methyl orange indicator. It is based on the color change of the TLC plate on reaction with formaldehyde. TLC plates impregnated with three kinds of solutions containing methyl orange, methyl yellow, mixing of methyl yellow and methyl orange were shown rectilinear response to formaldehyde concentration at constant exposure time. The color change of impregnated TLC plate with criteria air pollution, such as NO$_2$, SO$_2$, CO, $O_3$ was investigated. The color change of TLC plate with $O_3$ is larger than other gases.

• Journal of the Korean Institute of Gas
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• v.25 no.3
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• pp.27-38
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• 2021

We devised the system to automatically shutdown the boiler and to fundamentally block the harmful gases, including carbon monoxide, into the indoor when the exhaust system swerves: (1) The discharge pressure of the exhaust gas decreases when the exhaust pipe is disconnected. The monitoring system of the exhaust pipe is implemented by measuring the output voltage of APS(Air Pressure Sensor) installed to control the amount of combustion air. (2) The operating software was modified so that when the system recognizes the fault condition of a flue pipe, the boiler control unit displays the fault status on the indoor regulator while shutting down the boiler. In accordance with the ventilation facility standards in the "Rules for Building Equipment Standards" by the Ministry of Land, Infrastructure and Transport, experiments were conducted to ventilate indoor air. When carbon monoxide leaked in worst-case scenario, it was possible to prevent poisoning accidents. However, since 2013, the number of indoor air exchange times has been mitigated from 0.7 to 0.5 times per hour. We observed the concentration exceeding TWA 30 ppm occasionally and thus recommend to reinforce this criterion. In conclusion, if the flue pipe fault detection and the indoor air ventilation system are introduced, carbon monoxide poisoning accidents are expected to decrease significantly. Also when the manufacturing and inspection steps, the correct installation and repair are supplemented with the user's attention in missing flue, it will be served to prevent human casualties from carbon monoxide poisoning.

• Journal of the Korean Applied Science and Technology
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• v.39 no.2
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• pp.368-376
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• 2022

Spontaneous ignition occurs in industrial sites or anywhere in our lives, and is a phenomenon in which a substance ignites itself without an ignition source in the atmosphere. As the rate of chemical reaction increases, the heat generated increases, and the risk of spontaneous ignition increases. In this study, safe raw materials used for food and cosmetics were mixed to prepare coal spontaneous ignition prevention agents specifically among various spontaneous ignition phenomena. The effect of suppressing spontaneous combustion of coal was confirmed through lab and field tests with low-calorie, low-grade coal from Indonesia. As a result of the outdoor field test, the ignition prevention agent manufactured in this study compared with the control group(Fire after 90 days) showed excellent ignition inhibitors for more than 120 days. In addition, CO concentration control was confirmed by comparing the concentration of carbon monoxide for 50 days at the indoor coal yard. It was confirmed that the results were better than the comparative group coal and the existing anti-firing method. In addition, the possibility of coal fire prevention agents for indoor coal farms will be applied from 2024 was confirmed by studying the environment and safety of workers' working environments through official test such as soil and water quality test, MSDS of coal fire prevention agents in consideration of working workers, water quality, and eye irritation tests.

• Journal of Environmental Health Sciences
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• v.46 no.6
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• pp.627-635
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• 2020

Objectives: Indoor air quality has become more important aspeople spend most of their times indoors. Since students spend most of their times at home or at school, they are more likely to be exposed to indoor air pollutants. Ventilation in school classrooms can affect health and learning performance. In this study, ventilation deficiency was evaluated in school classrooms using Monte Carlo simulation. Methods: This study used sensor-based monitoring for six months to measure carbon dioxide (CO2) concentrations in classrooms in elementary, middle, and high schools. The volume of the classroom and the number of students were investigated, and the students' body surface area was used to calculate the CO2 emission rate. The distribution of ventilation rates was estimated by measured CO2 concentration and a mass-balance model using Monte Carlo simulation. Results: In the elementary, middle, and high schools, the average CO2 concentrations exceeded 1000 ppm, indicating that the ventilation rates were insufficient. The ventilation rates were deficient from July to August and in December, but showed relatively high ventilation rates in October. Forty-three percent of elementary schools, 56% of middle schools, and 62% of high schools showed insufficient ventilation rates. Conclusions: The ventilation rates calculated in elementary, middle and high schools were found to be quite insufficient. Therefore, proper management is needed to overcome the lack of ventilation and improve air quality.

• Particle and aerosol research
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• v.8 no.1
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• pp.9-15
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• 2012

Three different commercial particle counters were used to measure the PM2.5 particles in this study. An Aerosol Spectrometer (AS) 1.109 model of Grimm and a Particle Sensor (PS) 3030 model of HCT were compared with an Aerodynamic Particle Sizer (APS) 3321 model of TSI. The responses of these instruments were compared for four sizes ($1.0{\mu}m$, $1.5{\mu}m$, $2.0{\mu}m$ and $2.5{\mu}m$) of polystyrene latex (PSL) particles and indoor air particles of the office room. The mode diameter, particle size distribution and total particle number concentration of PSL particles were measured by each instrument. In the office room, the total particle number concentration was measured for 25 minutes. In results of particle size distribution and mode diameter, the APS 3321 (52 size-channels) was more accurate than the AS 1.109 (31 size-channels) and PS-3030 (10-szie channels) since the APS has more number of size-channels than the other instruments. However, AS 1.109 and PS-3030 provided similar results of total particle number concentration to those from the APS 3321. In results of office room test, there were no significant difference from each instrument similar to results of PSL test.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.3
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• pp.57-69
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• 2014

As of 2013, Korean population density is 505 persons per $1km^2$ and is ranked 3rd place in the most densely populated countries exception of city-states. It shows clearly the population is concentrated in the city area. To fulfil this urban concentration population demand, the enlargement and complexation of buildings, subway and other underground spaces connection tendency has been intensified, and it is need to construct the indoor spatial information DB as well as the accurate indoor surveying DB to promote people's safety and social welfare. In this study, Sadang station and Incheon National Airport were aimed for the construction of Wi-Fi AP location DB and RadioMap DB by collecting the indoor AP raw datas by using mobile device and those collected results were ran through the process of verification, supplementation, and analyzation. To evaluate the performance of constructed DB, 10 points in Incheon Airport- 3rd flr in block A, and 9 points in Sadang station-B1 were selected and calculated the estimated points and ran evaluation experiment using survey positioning error, which is distance between real position and the estimated position. The result shows that Incheon international airport's average and standard deviation was separately 17.81m, 17.79m and Sadang station's average and standard deviation was separately 22.64m, 23.74m. In Sadang station's case, the areas near the exit has low performance of surveying position due to fewer visible AP points than other areas. As total datas were examined except those position, it was verified that the user's location was mapping close position in surveying positioning by using constructed DB. It means that constructed DB contains correct Wi-Fi AP locations and radio wave patterns in object region, so it is considered that the indoor spatial information service based on constructed DB would be available.

• Particle and aerosol research
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• v.18 no.3
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• pp.51-59
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• 2022

In this work, virion concentration and its dose changes by HVAC and air cleaners were estimated in a subway station platform to control airborne infection of SARS-CoV-2. Collection efficiencies with particle size were measured for the air filter equipped in a HVAC in one subway station in Daejeon. Indoor PM_2.5 changes according to outdoor PM_2.5 with time were also measured to estimate air infiltration rate in the subway station platform. When infected persons generate virions by 10⁴, 10⁵, 10⁶, 3 × 10⁶ and 5 × 10⁶ h^-1 in a 2,400 m³ volume platform, the concentration and dose were estimated as 9, 92, 275 and 458 virions/m³ and 4, 43, 130 and 217 virions after 1 hour exposure, respectively. The concentration and dose were reduced by 70%, and 64%, respectively by operations of both HVAC (with a flow rate of 16,000 m³/h, MERV 11) and ten air cleaners(with total CADR 10,740 m³/h) compared to those without operation of both HVAC and air cleaners. However, virion dose in the platform was estimated to be too low at the general conditions due to a large space, a high air infiltration (3 h^-1) and a short residence time (usually < 10 mins) in the platform irrespective of the operations of HVAC or air cleaners. HVAC with filters and air cleaners would be more necessary in the concourse or shopping areas in the subway stations to reduce the infection dose from a few hundred to several tens virions in a hour.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.1
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• pp.1-10
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• 2006

Concentration and identification of airborne bacteria in the regulated public facilities were examined with the six-stage cascade impactor. Geometric mean total and respirable concentrations of airborne bacteria were $404cfu/m^3$ and $194cfu/m^3$ in hospital, $931cfu/m^3$ and $358cfu/m^3$ in kindergarten, $294cfu/m^3$ and $134cfu/m^3$ in day-care center, and $586cfu/m^3$ and $254cfu/m^3$ in postpartum nurse center, respectively. As a result, culturable total and respirable concentrations of airborne bacteria were significantly highest in kindergarten and lowest in day-care center (p<0.05). The ratio of respirable to total concentration of airborne bacteria in the investigated public facilities was ranged from 30% to 40% but there was no significant difference among them (p>0.05). The mean I/O ratio of culturable total and respirable concentrations were 0.58 and 0.66 in hospital, 0.71 and 0.83 in kindergarten, 0.28 and 0.41 in day-care center, and 0.63 and 0.78 in postpartum nurse center, respectively. Day-care center showed the lowest I/O ratio of culturable total and respirable concentration of airborne bacteria (p<0.05) but a significant difference was not found among other facilities. Indoor concentration of airborne bacteria did not correlated significantly with indoor temperature and relative humidity (p>0.05) but had a significant positive correlation with $CO_2$ and surrounding condition (p<0.05). Staphylococcus spp., Micrococcus spp., Corynebacterium spp., and Bacillus spp. were dominant genera and amounted to over 95% of total airborne bacteria identified in the investigated public facilities. Size distributions of four dominant genera did not observed inconsistently regardless of type of public facility.

• Journal of the Korean Society for Railway
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• v.20 no.1
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• pp.11-19
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• 2017

Since operation of railway trains is a major source of particle pollution in tunnel air, a particle removal device can be an effective measure to remove wear particles. To obtain design conditions of the particle removal device that will be installed underneath the railway trains, the wind speed and particle concentration underneath the trains were investigated using a three-dimensional ultrasonic anemometer and a DustTrak aerosol monitor, respectively. The measurements were made for the trains running on Seoul Metropolitan Subway Line 5 on February 10, 2015. The data were analyzed according to the track geometry (straight, curved) and train speed pattern (acceleration, cruising, and deceleration) between stations. Train speed was also analyzed. The average wind speed and $PM_{10}$ concentration underneath the trains were ~30% of the train speed and ${\sim}200{\mu}g/m^3$ for both straight and curved sections. Average $PM_{10}$ concentration for deceleration sections was higher than that for acceleration sections.