Influence of CYP1A2 and NAT2 Metabolic Phenotypes on Smokers' Urinary Mutagenicity

The influence of the metabolic phenotypes NAT2 and CYP1A2 on urinary mutagenicity of 118 smokers was studied. Mutagenicity of urine samples was determined by Ames test (preincubation plate incorporation assay on YG1024 Salmonella typhimurium strain with S9 mix). Urinary nicotine plus its metabolites were determined to check cigarette smoke intake. The N -acetyltransferase (NAT2) and cytochrome P450 1A2 (CYP1A2) phenotypes were measured by the molar ratio of urinary caffeine metabolites, determined by HPLC analysis. Urinary mutagenicity was significantly higher in smokers CYP1A2 extensive (EM) than in CYP1A2 poor metabolizers (PM) (Mann-Whitney U test, p = 0.020). Linear multiple regression analysis shows that an increase in urinary mutagenicity levels was significantly related to cigarette smoke intake and to CYP1A2 N -hydroxylation activity ( t = 5.06, p < 0.001, and t = 2.33, p = 0.021), but not to NAT2 acetylation phenotype. In conclusion, phenotypic differences in metabolic activation of tobacco smoke mutagens are able to modulate the presence of mutagens in urine of cigarette smokers and, consequently, the potential genotoxic risk.     

Characteristics of smoke extraction by natural ventilation during a fire in a shallow urban road tunnel with roof openings

The characteristics of the spread of smoke were investigated for a fire occurring in a shallow urban road tunnel with roof openings in its ceiling. In this type of tunnel, the smoke produced by a fire is ventilated through the openings in the ceiling given the natural buoyancy of hot smoke. A fire experiment was conducted using a 1/12 scale model tunnel to ascertain whether natural ventilation via the roof openings was sufficient to maintain a safe evacuation environment for tunnel users. The distance from the fire to the tip position of the spreading smoke and the thickness of smoke layers along the ceiling were investigated by changing the heat release rate and using two types of median structure as experimental parameters. The two types of median structure dividing the tunnel into two road tubes were pillars and walls. It was clarified that the smoke spreading distance was constant and independent of the heat release rate of the fire under our experimental conditions. Moreover, it was confirmed that the thickness of the smoke layers in the tunnel thinned out quickly due to the natural ventilation.     

Full-scale experiment and CFD simulation on smoke movement and smoke control in a metro tunnel with one opening portal

Three full-scale model experiments were conducted in a unidirectional tube, which is a part of a metro tunnel with one end connected to an underground metro station and the other end opened to outside in Chongqing, PR China. Three fire HRRs, 1.35 MW, 3 MW and 3.8 MW were produced by pool fires with different oil pan sizes in the experiments. Temperature distributions under the tunnel ceiling along the longitudinal direction were measured. At the same time, CFD simulations were conducted under the same boundary conditions with the experiments by FDS 5.5. In addition, more FDS simulation cases were conducted after the FDS simulation results agreed with the experimental results. The simulation results show that the smoke temperature and the decay rate of the temperature distribution under the tunnel ceiling along the longitudinal direction increase as HRR increases. The smoke exhausts effectively from the tunnel under mechanical ventilation system, whether the emergency vent is activated as a smoke exhaust or an air supply vent. The operation mode of the mechanical ventilation system depends on the evacuation route.     

模拟火灾用发烟剂的实验研究

对烟火类发烟剂的组成、工作原理、生产工艺流程及技术指标等作了简要阐述,并对近年来国内外烟火类发烟剂研究中存在的问题及今后的发展方向进行了探讨与展望。烟火类发烟剂既要满足消防演习等烟雾要求,又要具有较高的仿真性及安全性。     

高层建筑设置防排烟系统的重要性

通过对高层建筑防排烟系统重要性和防排烟形式的论述,提出了如何采取控烟措施,搞好防排烟系统的设计与施工,提高人们防排烟系统的认识,具有深远意义。     

Characterization of molecular markers in smoke from residential coal combustion in China

The organic constituents and distributions of molecular markers emitted from a residential coal-stove burning honeycomb coal briquettes were determined in this study. The major organic components emitted directly in smoke particles were polycyclic aromatic hydrocarbons (PAHs), with abundant hydroxy-polycyclic aromatic hydrocarbons (OH-PAHs), i.e., thermally altered derivative compounds from coal combustion, UCM (unresolved complex mixture of branched and cyclic compounds), n-alkanes and n-alkanoic acids. Other compounds present as minor components included n-alkenes, phenols, alkylbenzenes and n-alkanols. The distributions of the organic compounds in the coal smoke samples were highly variable and dependent on combustion temperature, flame aeration, fire duration, and coal rank. Coal smoke emissions may be identified by some indicators including: (1) presence of hydroxy-PAHs, (2) the decrease in carbon preference index (CPI) of n-alkanoic acids with increasing rank, (3) the decrease of the ratios of 17α(H),21β(H)-29-norhopane to 22R-17α(H),21β(H)-homohopane and 17α(H),21β(H)-29-norhopane to 17α(H),21β(H)-hopane with increasing rank, (4) the increases in the homohopane index [22S/(22S + 22R)] and the 17α(H),21β(H)-hopane to 17β(H), 21α(H)-hopane ratio with increasing rank, and (5) the increase of benzo[e]pyrene/(benzo[e]pyrene + benzo[a]pyrene) with increasing rank. In addition, the diagnostic ratios among PAHs and between PAHs and the corresponding hydroxy-PAHs, such as benz[a]anthracene/(benz[a]anthracene + chrysene), indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene + benzo[ghi]perylene), pyrene/OH-pyrene, and chrysene/OH-chrysene can be used to distinguish bituminous from anthracite coal smoke emissions.     

A study of an optimal smoke control strategy for an Urban Traffic Link Tunnel fire

An Urban Traffic Link Tunnel (UTLT) is a novel type of underground transportation system consisting of a main tunnel in a loop shape and several linked tunnels. It has a higher level of fire risk compared to other common road tunnels. In this study, numerical study was conducted to investigate the smoke control strategies for a designed fire scenario in the Beijing Center Business District (CBD) UTLT. An optimal smoke control strategy was developed and evaluated using three criteria: critical velocity, minimal smoke spreading area and available safe evacuation time. In developing the optimal smoke control strategy, six different smoke control strategies for the UTLT were evaluated initially by the criterion of critical velocity, and one of those control strategies was chosen as the primary strategy by steady simulation. This strategy was then modified according to the dynamic simulated results of smoke movements to satisfy the other two criteria. Consequently, the optimal smoke control strategy for the UTLT based on the primary strategy was obtained. The transient distributions of the smoke spread, smoke temperature and CO₂ concentration, were analyzed.     

Movement speed and exit choice in smoke-filled rail tunnels

An evacuation experiment including 100 individuals was performed inside a tunnel in order to study the effectiveness of different way-finding installations and to collect data on movement speeds and human behaviour. The participants took part in the experiment individually, and no group interactions were studied. The experiment tunnel was 200 m long and an emergency exit was located 180 m into the tunnel. In addition, emergency signs including distances to nearest exits were located every eight meters on both sides of the tunnel. The tunnel was filled with artificial smoke and acetic acid, which produced a mean light extinction coefficient of 2.2 m⁻¹. Participants had been told that they would participate in an evacuation experiment, but they had not been informed about the layout of the tunnel or the technical installations. The average movement speed was found to be approximately 0.9 m/s, independent of tunnel floor material examined. The experiment also demonstrated the importance of the emergency exit design. A loudspeaker, which provided people with an alarm signal and a pre-recorded voice message, was found to perform particular well in terms of attracting people to the exit, independent of which side of the tunnel the participants were following.     

吸气式感烟探测报警系统的应用

主要探讨高灵敏度吸气式感烟探测报警系统在设置条件及设置方式等方面的应用依据，并提出一个应用方法。     

Corrosive effects of smoke with different concentrations from PVC on 304 stainless steel and 6061 aluminium alloy

Three hundred and four stainless steel and 6061 aluminium alloy samples were exposed to different concentrations of smoke generated by polyvinyl chloride in high humidity. The corrosion kinetics of 304 stainless steel and 6061 aluminium alloy under smoke were found to obey the power function and a linear rule, respectively. Pitting corrosion in smoke became increasingly obvious with exposure time. Surface morphology and chemical compositions of corrosion products were analysed by scanning electron microscope, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. Possible corrosion mechanisms were proposed and compared. All the analysis helps to provide basic information for the determination of smoke damage and timely rescue after fire.