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真空泵的工作原理
作者：德尔塔 日期：2022-05-04
是用各种方法在某一封闭空间中产生、改善和维持真空的装置。真空泵可以定义为：利用机械、物理、化学或物理化学的方法对被抽容器进行抽气而获得真空的器件或设备。随着真空应用的发展，真空泵的种类已发展了很多种，其抽速从每秒零点几升到每秒几十万、数百万升。按真空泵的工作原理，真空泵基本上可以分为两种类型，即气体传输泵和气体捕集泵。随着真空应用技术在生产和科学研究领域中对其应用压强范围的要求越来越宽，大多需要由几种真空泵组成真空抽气系统共同抽气后才能满足生产和科学研究过程的要求，由于真空应用部门所涉及的工作压力的范围很宽，因此任何一种类型的真空泵都不可能完全适用于所有的工作压力范围，只能根据不同的工作压力范围和不同的工作要求，使用不同类型的真空泵。为了使用方便和各种真空工艺过程的需要，有时将各种真空泵按其性能要求组合起来，以机组型式应用。 各种的工作原理 /液环工作原理 （简称）是一种粗，它所能获得的极限真空为2000~4000Pa，串联大气喷射器可达270~670Pa。也可用作压缩机，称为水环式压缩机，是属于低压的压缩机，其压力范围为1~2×105Pa表压力。 最初用作自吸水泵，而后逐渐用于石油、化工、机械、矿山、轻工、医药及食品等许多工业部门。在工业生产的许多工艺过程中，如真空过滤、真空引水、真空送料、真空蒸发、真空浓缩、真空回潮和真空脱气等，水环泵得到广泛的应用。由于真空应用技术的飞跃发展，在粗真空获得方面一直被人们所重视。由于中气体压缩是等温的，故可抽除易燃、易爆的气体，此外还可抽除含尘、含水的气体，因此，应用日益增多。 在泵体中装有适量的水作为工作液。当叶轮按图中顺时针方向旋转时，水被叶轮抛向四周，由于离心力的作用，水形成了一个决定于泵腔形状的近似于等厚度的封闭圆环。水环的下部分内表面恰好与叶轮轮毂相切，水环的上部内表面刚好与叶片顶端接触（实际上叶片在水环内有一定的插入深度）。此时叶轮轮毂与水环
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真空泵的机械安装注意事项
作者：德尔塔 日期：2022-05-04
安装原理图 1、真空泵应安装在地面结实坚固的场所，周围应留有充分的余地，便于检查、维护、保养。 2、真空泵底座下应保持地基水平，底座四角处建议垫减震橡皮或用螺栓浇制安装，确保真空泵运转平稳，振动小。 3、真空泵与系统的连接管道应密封可靠，对小真空泵可采用金属管路连接密封垫采用耐油橡胶，对小真空泵可采用真空胶管连接，管道管径不得小于真空泵吸气口径，且要求管路短而少弯头。（焊接管路时应清除管道中焊渣，严禁焊渣进入真空泵腔。） 4、在连接管路中，用户可在真空泵进气口上方安装阀门及真空计，随时可检查真空泵的极限压力。 5、按电动机标牌规定连接电源，并接地线和安装合适规格的熔断器及热继电器。 6、真空泵通电试运转时，须取下电机皮带，确认真空泵转向符合规定方向方可投入使用，以防真空泵反转喷油。（转向按防护罩指示方向） 7、对于有冷却水的真空泵，按规定接通冷却水。 8、如真空泵口安装电磁阀时，阀与真空泵应同时动作。 9、当真空泵排出气体影响工作环境时，可在排气口装接管道引离或装接油雾过滤器.
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磁力泵工作原理
作者：德尔塔 日期：2022-05-04
磁力泵由泵、磁力传动器、电动机三部分组成。关键部件磁力传动器由外磁转子、内磁转子及不导磁的隔离套组成。当电动机带动外磁转子旋转时，磁场能穿透空气隙和非磁性物质，带动与叶轮相连的内磁转子作同步旋转，实现动力的无接触传递，将动密封转化为静密封。由于泵轴、内磁转子被泵体、隔离套完全封闭，从而彻底解决了“跑、冒、滴、漏”问题，消除了炼油化工行业易燃、易爆、有毒、有害介质通过泵密封泄漏的安全隐患，有力地保证了职工的身心健康和安全生产。 一、磁力泵工作原理 将n对磁体（n为偶数）按规律排列组装在磁力传动器的内、外磁转子上，使磁体部分相互组成完整藕合的磁力系统。当内、外两磁极处于异极相对，即两个磁极间的位移角Φ＝0，此时磁系统的磁能最低；当磁极转动到同极相对，即两个磁极间的位移角Φ＝2π/n，此时磁系统的磁能最大。去掉外力后，由于磁系统的磁极相互排斥，磁力将使磁体恢复到磁能最低的状态。于是磁体产生运动，带动磁转子旋转。 二、结构特点 1．永磁体 由稀土永磁材料制成的永磁体工作温度范围广(-45－400℃)，矫顽力高，磁场方向具有很好的各向异性，在同极相接近时也不会发生退磁现象，是一种很好的磁场源。 2.隔离套 在采用金属隔离套时，隔离套处于一个正弦交变的磁场中，在垂直于磁力线方向的截面上感应出涡电流并转化成热量。涡流的表达式为： 。其中Pe－涡流；K—常数；n—泵的额定转速；T－磁传动力矩；F－隔套内的压力；D－隔套内径； 一材料的电阻率； —材料的抗拉强度。当泵设计好后，n、T是工况给定的，要降低涡流只能从F、D、 、 等方面考虑。选用高电阻率、高强度的非金属材料制作隔离套，在降低涡流方面效果十分明显。 3．冷却润滑液流量的控制 泵运转时，必须用少量的液体对内磁转子与隔离套之间的环隙区域和滑动轴承的摩擦副进行冲洗冷却。冷却液的流量通常为泵设计流量的2%-3%，内磁转子与隔离套之间的环隙区域由于涡流而产生高热量。当
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Ex Vivo Human Primary Mesenchymal Stem Cells (MSCs) Culture
作者：德尔塔 日期：2022-05-04
Ex Vivo Human Primary Mesenchymal Stem Cells (MSCs) Culture Human bone marrow contains mesenchymal progenitors (mesenchymal stem cells, MSCs). MSCs produce adventitial cells in the human bone marrow microenvironment. MSCs are multipotent stem cells that can differentiate into a variety of cell types, including: osteoblasts (bone cells), chondrocytes (cartilage cells) and adipocytes (fat cells). These cells provide support to hematopoiesis by producing membrane-bound and soluble signals and cytokines. These stromal progenitors can be readily isolated from bone marrow and demonstrate extensive proliferative capacity in vitro. Purified and culture-expanded human MSCs differentiate along the osteogenic, chondrogenic, and adipogenic lineages both in vitro and in vivo. Materials and Methods 1. On enrollment, approximately 35 days before scheduled peripheral-blood progenitor-cell (PBPC) infusion, 20 to 25 ml of bone marrow aspirate was obtained. 2. Aspirates were obtained 2 to 48 hours before high-dose cyclophosphamide mobilization chemotherapy. 3. The aspirate was taken to the class 10,000 quality clean production suite. 4. Aspirate was mixed with two volumes of Dulbecco’s phosphate-buffered saline (DPBS) in a sterile class II biologic safety cabinet and centrifuged at 900 x g for 10 minutes at 20°C in a Beckman GS-6R centrifuge. 5. Pellets were layered onto 25 mL of Percoll (density, 1.073 g/ml) at a density of 1 to 2 x 107 cells/ml. 6. Gradients were centrifuged at 900 x g for 30 minutes at 20°C, and recovered mononuclear cells were resuspended in DPBS and centri
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Isolation and Culture of Multipotent Stem Cells from Human Bone Morrow
作者：德尔塔 日期：2022-05-04
Isolation and Culture of Multipotent Stem Cells from Human Bone Morrow Bone marrow contains three types of stem cells: 1. Hematopoietic stem cells give rise to the three classes of blood cells that are found in the circulation: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes). 2. Mesenchymal stem cells are found arrayed around the central sinus in the bone marrow. They have the capability to differentiate into osteoblasts, chondrocytes, myocytes, and many other types of cells. They also function as "gatekeeper" cells of the bone marrow. 3. Endothelial stem cells The bone marrow stroma contains mesenchymal stem cells (also called marrow stromal cells). These cells are multipotent stem cells that can differentiate into a variety of cell types. Cell types that MSCs have been shown to differentiate into in vitro or in vivo include osteoblasts, chondrocytes, myocytes, adipocytes, and, as described lately, beta-pancreatic islets cells. They can also trans-differentiate into neuronal cells. Materials and Methods 1. Fresh unprocessed human bone marrow (BM) from young male donors was isolated. 2. BM was centrifuged at 350 g for 10 minutes to obtain cell pellets, which then were resuspended in 25 ml of Dulbecco’s PBS (DPBS) containing 0.5 M EDTA. 3. After centrifugation at 350 g for 7 minutes, the cells were resuspended in 5 ml DPBS containing 0.5 M EDTA and 20 ml of NH4Cl for induction of hemolysis. 4. After centrifugation and washing with DPBS containing 0.5 M EDTA, cells were filtered through a 40-μm nylon filter and plat
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Isolation and Culture of Human Liver Stem Cells
作者：德尔塔 日期：2022-05-04
Isolation and Culture of Human Liver Stem Cells Materials and Methods 1. Human hepatocytes were isolated from fresh surgical specimens of patients undergoing hepatectomies. Healthy liver tissue (5–20g) was used to isolate hepatocytes by collagenase digestion. 2. Liver tissues were isolated and perfused with 350 ml of a warm (37°C) calcium-free buffer. 3. Liver tissues were digested in Digest Medium at 37°C. This resulted in blanching, softening, and dissociation of hepatic tissue and provided complete digestion of the liver in 10–12 minutes. 4. The hepatocytes were released by mincing and pipetting with a large-bore pipette. 5. The cell suspension was filtered through a sterile 100-μm nylon mesh into a beaker placed on ice, sedimented by centrifugation at 50g for 5 minutes, resuspended, and washed two to three times in cold wash medium. 6. The initial plating consisted of Williams Medium E supplemented with glutamine and with 5% fetal calf serum. 7. Unattached cells were poured off 2–3 hours later and replaced with hepatocyte serum-free medium, a highly modified Chees' medium supplemented with 1.25 μg/cm2 collagen to provide a sandwich matrix. 8. Cultures were re-fed with Hepatozyme-SFM (without collagen) at 24 hours and every 48 hours thereafter. 9. Hepatocytes were seeded at a density of 1.0–1.5 × 105 viable cells, 80% viable cells determined by the trypan blue, per cm2 onto collagen-coated culture plates in Hepatozyme-SFM maintained at 37°C, 5% CO2 for 2 weeks. 10. Human cryopreserved normal hepatocytes obtained were also used. 11. After 2 weeks of culture,
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Identification and expansion of the tumorigenic lung cancer stem cell population
作者：德尔塔 日期：2022-05-04
Identification and expansion of the tumorigenic lung cancer stem cell population Lung cancer contains a rare population of CD133+ cancer stem-like cells able to self-renew and generates an unlimited progeny of non-tumorigenic cells. The current technology allows the establishment of long-term lung cancer stem cell cultures from about one-third of the tumors. 1. Tumor samples were obtained. 2. Surgical specimens were washed several times and left overnight in culture system. DMEM–F12 medium supplemented high doses of penicillin/streptomycin amphotericin B 3. Tissue dissociation was carried out by enzymatic digestion (20 μg/ml collagenase II) for 2 h at 37°C. 4. Recovered cells were cultured at clonal density in serum-free medium. 50 μg/ml insulin 100 μg/ml apo-transferrin 10 μg/ml putrescine 0.03 mM sodium selenite 2 μM progesterone 0.6% glucose 5 mM HEPES 0.1% sodium bicarbonate 0.4% BSA glutamine and antibiotics 20 μg/ml EGF 10 μg/ml bFGF. 5. Flasks non-treated for tissue culture were used to reduce cell adherence and support growth as undifferentiated tumor spheres. 6. The medium was replaced or supplemented with fresh growth factors twice a week until cells started to grow forming floating aggregates. 7. Cultures were expanded by mechanical dissociation of spheres, followed by re-plating of both single cells and residual small aggregates in complete fresh medium. 8. Stem cell medium was replaced with Bronchial Epithelial Cell Growth Medium in tissue culture-treated flasks. 9. Identification: Antibodies used were PE-
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Isolation and Culture of Human Brain Tumor Stem Cell
作者：德尔塔 日期：2022-05-04
Isolation and Culture of Human Brain Tumor Stem Cell The isolation, culture, identification, and purification of stem cells from primary human brain tumors of different phenotypes have marked capacity for proliferation, self-renewal, and differentiation. These cells represents a minority of the tumor cell population and are identified by expression of the cell surface marker the positive CD133. These positive CD133 cells, termed the brain tumor stem cells (BTSCs), which are the expression of neural differentiation markers, and are necessary for the proliferation and self-renewal of the tumor in culture. 1. Tumor samples were obtained from the informed consenting patients. 2. Tumors were washed, acutely dissociated in oxygenated artificial cerebrospinal fluid and subject to enzymatic dissociation. 3. Tumor cells were then resuspended in tumor sphere medium (TSM) • Serum-free neural stem cell medium • Human recombinant EGF (20 ng/ml) • bFGF (20 ng/ml) • Leukemia inhibitory factor (10 ng/ml) • Neuronal Survival Factor (NSF) (10 ng/ml) • N-acetylcysteine (60 μg/ml) 4. Plated at a density of 3 × 106 live cells/60-mm plate. 5. RBCs were removed using lympholyte-M. 6. After primary sphere formation was noted, sphere cells were dissociated and plated in 96-well microwell plates in 0.2 ml volumes of TSM. 7. Final cell dilutions ranged from 200 cells/well to 1 cell/well in 0.2-ml volumes. 8. Cultures were fed 0.025 ml of TSM every 2 days until day 7, when the percentage of wells not containing spheres for each cell plating density was calculated and
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Measurement of primary endothelial cell permeability to fluxes of dextran or albumin
作者：德尔塔 日期：2022-05-04
Measurement of primary endothelial cell permeability to fluxes of dextran or albumin The fluxes of albumin or dextran across vascular endothelial cell (ECs) were evaluated using Transwell chambers. Both molecules were measured for the following reasons: 1) they have different sizes, with albumin having a molecular mass of ∼65 kDa and dextran ∼10 kDa; 2) they may use different transport mechanisms across ECs. In addition to pinocytotic and intercellular transport, albumin transport can be modulated by albumin-binding proteins present on the EC surface. ECs were seeded onto Transwell inserts (6.5-mm diameter and 0.4-µm pore size) coated with 12.5 µg/ml fibronectin. One hour later, 0.05 µCi of 125I-labeled human albumin (Iso-Tex Diagnostics) and 250 µg of FITC-conjugated dextran (10 kDa) were added to the top well, and 100-µl aliquots of samples were taken from the bottom chamber every 15 min for 2 h. The amounts of albumin and dextran in the samples were measured using a gamma counter and a fluorescence plate reader. Each time after taking a sample, 100 µl of medium was added back to the bottom chamber. For each time point, the amounts of albumin and dextran present in the bottom wells as well as the amounts in all the samples removed for measurement were calculated, added up, and plotted. In every experiment, fibronectin-coated filter inserts without ECs were included, and the amounts of dextran and albumin in the bottom wells in each sample were expressed relative to the amounts of these two molecules in
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Primary Culture of Pulmonary Arterial Smooth Muscle Cells
作者：德尔塔 日期：2022-05-04
Primary Culture of Pulmonary Arterial Smooth Muscle Cells 1.Primary cultures of Pulmonary Arterial Smooth Muscle Cells (PASMCs) were isolated from human main pulmonary artery. 2.A segment of the main pulmonary artery was excised and placed in a sterile 10-cm dish containing primary cell culture media. 3.The segment was stripped of adventitia with a sterile forceps. 4.The main pulmonary artery segment was then cut longitudinally to open the vessel, and the endothelial layer was removed by gentle rubbing with a cell scraper. 5.The vessel was then cut into 2-mm segments, inverted, and placed on a collagen-coated 35-mm tissue culture dish. 6.A drop of primary cell culture media containing 10% fetal bovine serum, primary cell culture supplements, antibiotics, and antimycotics was then added, and the cells were grown overnight at 37°C in a humidified atmosphere with 5% CO2-95% air. 7.The next day, an additional 2 ml of complete medium were added. 8.The growth medium was subsequently changed every 2 days. 9.When SMC islands could be observed under the microscope, the tissue segment was removed and the individual cell islands were subcloned. 10.Identity was confirmed as PASMCs by immunostaining (>99% positive) with SMC actin. This was taken as evidence that cultures were not contaminated with fibroblasts or endothelial cells. 11.All cultures for subsequent experiments were maintained in primary cell culture media containing 10% fetal bovine serum, primary cell culture supplements, antibiotics, and antimycotics at 37°C in a humidified atmosphere with
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《Science》发表非损伤微测技术研究Ca2+流速的成果
作者：德尔塔 日期：2022-05-04
D型丝氨酸调节谷氨酸受体基因构成的Ca2+通道 2011年3月17日，葡萄牙里斯本大学José Feijó教授的研究成果在世界知名杂志《Science》以“Research Article”的形式在线发表，中国农业大学资源环境学院的刘来华教授参与了本项研究。细胞内游离Ca2+的增加构成了真核细胞基本的信号转导机制，但是Ca2+通道蛋白如何启动信号一直存在争论。 在这项研究中科学家使用非损伤微测技术（vibrating microelectrodes or NMT）测定了氨基酸刺激后花粉管的Ca2+流动，直接证实了植物中具有和动物中相似的神经传递系统。发现谷氨酸受体类似基因（GLRs）减少了通过质膜的Ca2+内流，进而调节花粉管顶端胞质中的Ca2+浓度梯度，最终影响花粉管的生长和形态建成。此外，敲除花粉管丝氨酸消旋酶（SR1的突变体）后GLRs活性下降，导致生长发生缺陷。这项研究揭示了氨基酸调节雄性配子体和雌蕊组织之间全新的信号转导机制，类似于动物神经系统的常见机制。这不仅是植物学的重大发现，对动物学、医学等其他领域的研究也具有很大的参考价值。 非损伤微测技术（NMT，）是一种活体研究技术，无需标记就可以实时地获取离子和小分子的流速，是研究活体信号转导和神经传递系统的最佳手段之一。José Feijó实验室近年来使用非损伤微测技术在高水平杂志发表了多篇论文。本次发表的论文是该实验室研究工作的代表，也标志着非损伤微测技术的应用越来越广泛，产生的成果越来越有影响力。 关键词：谷氨酸受体类似基因（Glutamate Receptor–Like Genes，GLRs）；钙离子通道（Ca2+ Channel）；花粉管（Pollen Tube）；D型丝氨酸（D-Ser） 参考文献：Michard E et al. Science, DOI: 10.1126/science.1201101 链接：
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超声波传感器对液体进行智能检测
作者：德尔塔 日期：2022-05-04
在实验室自动化中要用到大量的微生物培养用孔板和试管对液体进行分析。采用新的超声传感器，能够快速地、以精确到0.1 mm的精度完成液位高度检测。 实验室也开始越来越多地利用自动化设备来完成试验、检验的任务了，例如：检验分析试剂、试样的吸移等等。而在这些工作中所使用的传感器应该能够精准地进行工作，并提供具有可追溯性的结果，同时还必须具有很高的检测速度。举个例子来说，在一个液体介质检查工位上，很重要的一个步骤就是向很小的玻璃试管灌装检验分析用的液体介质，例如灌入需要分析的血液。在把少量的检测试样灌入到微小的试管中之后，在检验分析开始之前，需要对微小试管中液体介质的液位高度进行检测。这些微小的微生物培养器皿的开口很小，有些微生物培育瓶的口径只有3 mm，但仍然要求传感器能够在最短的时间内精确地检测出瓶内液体介质的容量。当前使用的电容式检测技术还达不到理想的检测精度。一个个独立设置的光电式传感器虽然满足了检测精度的要求，但是价格不菲。 超声传感器是一种完全不与被接触介质接触的检测传感器。这一特性在实验室应用中非常有意义：既保证了传感器不被腐蚀，也保证了被测介质不会出现交叉污染。另外，超声波传感器还对周围环境的湿度和灰尘非常不敏感，从而也保证了它们能够长期、稳定地准确工作。 与光电式传感器相比较，超声式传感器不产生光线，而是利用声波进行检测的，因此它能够可靠地检测不同性质的介质，而且与被测介质的透明度和颜色无关。不论被测介质的粘度高低如何，都不会对检测结果产生影响。 连续工作的超声波传感器向被测对象发射出锥形的声波。这束锥形声波恰好可以进入口径不足10 mm的瓶口，对瓶内的液位高低进行检测。为了避免在使用时受到其他因素的限制，生产厂家与用户密切结合，研发出了新型09系列的超声波传感器。这种新型超声波传感器配备了特殊设计的超声波发射嘴，使发射出去的超声波波束直径更小，能够进入口径3 mm的培育瓶
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接触角测量技术原理及其应用领域
作者：德尔塔 日期：2022-05-04
What is contact angle? Contact angle ,θ , is a quantitative measure of the wetting of a solid by a liquid. It is defined geometrically as the angle formed by a liquid at the three phase boundary where a liquid, gas and solid intersect as shown below: It can be seen from this figure that a low values of contact angle (θ) indicates that the liquid spreads, or wets well, while a high contact angle indicates poor wetting. If the angle θ is less than 90 degrees the liquid is said to wet the solid. If it is greater than 90 degrees it is said to be non-wetting. A zero contact angle represents complete wetting. The measurement of a single static contact angle to characterize the interaction is no longer thought to be adequate. For any given solid/ liquid interaction there exists a range of contact angles which may be found. The value of static contact angles are found to depend on the recent history of the interaction. When the drop has recently expanded the angle is said to represent the ‘advanced’ contact angle. When the drop has recently contracted the angle is said to represent the ‘receded’ contact angle. These angles fall within a range with advanced angles approaching a maximum value and receded angles approaching a minimum value. If the three phase (liquid/solid/vapor) boundary is in actual motion the angles produced are called Dynamic Contact Angles and are referred to as ‘advancing’ and ‘receding’ angles. The difference between ‘advanced’ and ‘advancing’, ‘receded’ and ‘receding’ is that in the static case motion is incipient in the dynamic case motion is actual. D
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Isolation of Human Pulmonary Epithelial Cells
作者：德尔塔 日期：2022-05-04
Isolation of Human Pulmonary Epithelial Cells 1. Pulmonary epithelial cells from human lung tissue were isolated. 2. Lungs were perfused with 10 ml of primary cell medium (supplemented with 1% antibiotics and 2 mM L-glutamine) through the pulmonary artery until they were cleared of blood. 3. Bronchoalveolar lavages were performed using 5 × 1 ml of PBS, 1 mM EDTA to remove alveolar leukocytes. 4. One ml of primary cell isolation solution was instilled into the lungs through the trachea. 5. Lungs were then removed and placed in a sterile tube containing 2 ml of primary cell medium (supplemented with 1% antibiotics and 2 mM L-glutamine) and incubated at 4 °C overnight for enzymatic digestion to occur. 6. Lung tissues were further teased apart in primary cell medium, 10% FCS in a dish. 7. The cell isolate was passed through a 100-μm filter, and pulmonary epithelial cells were purified as follows. 8. Collected cells were counted and incubated for 15 min at 4 °C at the appropriate ratios. 9. Cells were then washed and diluted in primary cell medium, 0.5% FCS. 10. Pulmonary epithelial cells thus obtained were plated on 6-well plate (4 × 105 cells/well) in primary cell medium, 10% FCS.
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环境气体浓度的表示方法及有限空间内的中毒危害
作者：德尔塔 日期：2022-05-04
环境气体浓度的表示有很多种不同的方法，在这里做下简单介绍： WA:时间加权浓度,是污染物在指定时间段内的平均浓度； REL：建议浓度限值，每周四十小时工作制，每天最高十小时TWA允许浓度； PWL：允许的浓度值限制，TLV是阈限值，是TWA的允许浓度，对于每周四十小时，每天八小时的正常工作制来说，工人可以在该浓度下连续工作与气体发生接触而不会产生影响； STEL：短期暴露极限值，定义为十五分钟TWA暴露，在一个工作日的任何时候均不得超过该限值，即使八小时TWA处于限值范围内； IDLH：立即危险浓度，不得超过的最高环境浓度，超过后必须采取高可靠性防毒面具。 有毒有害物质可以是原来就存在于有限空间内的，也可以是作业过程中逐渐积聚的，比较常见的有： (1)苯、甲苯、二甲苯。如在有限空间内进行防腐涂层作业时，由于涂料中含有的苯、甲苯、二甲苯等有机溶剂的挥发，造成有毒物质的浓度逐步增高等。 (2)硫化氢。如清理、疏通下水道、粪便池、窑井、污水池、地窖等作业容易产生硫化氢。 (3)一氧化碳。如在市政建设、道路施工时，损坏煤气管道，煤气渗透到有限空间内或附近民居内，造成一氧化碳积聚，以及在设备检修时，设备内残留的一氧化碳泄漏等。这些有毒有害气体检测要选择有毒气体检测仪。
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