Romeo L, Prigioni P, Marcheselli S, Marchiori L, Cerpelloni M, Fiorini C, Brugnone F
Medicina del Lavoro, Dipartimento di Medicina e Sanità Pubblica, Università degli Studi di Verona.
Med Lav. 2002 Jan-Feb;93(1):26-33.
Carbon dioxide (CO2), a very high density gas, tends to stratify at the lowest levels of the atmosphere. It can be produced by neutral geothermal emissions, fermentative processes or by human and industrial activity. When carbon dioxide concentrations rise to a very high level in a confined and poorly ventilated space, the anoxic hazard is a very important cause of severe accidents that can involve workers and rescuers. At CO2 levels higher than 20% there is a very high risk of a fatal accident, also considering the odourless feature of this gas.
Two fatal accidents in workers are described which occurred during inspection of a concrete well, built as a part of sewerage network in a rural area. In the weeks after the accident, composition and concentration of gases inside the well were analysed. We also considered the influence of an organic fertilizer called "pollina" which was found on the ground around the concrete well, in order to ascertain whether fermentation could alter the gas composition inside the well.
Samples of air and water were collected in the well and samples of the organic fertilizer (pollina) on the ground surrounding the concrete well were also taken. Different quantities of organic fertilizer (pollina) with or without water were incubated in airtight glass bottles and placed in a dark room at 20 degrees C temperature; analysis of air inside the glass bottles was performed after 7 and 18 days of incubation. All the samples of air and water were analysed by gas-chromatographic-mass-spectrometry.
Analysis of the air samples collected inside the well after 2, 16 and 18 weeks after the accident showed a low concentration of O2 (range 4.2-9%), a high concentration of CO2 (range 5.9-12.3%), a normal level of N2 (range 78-85%) and a concentration of N2O between 0.03 and 0.19%. In water collected 2 weeks after the accident at the bottom of the concrete well, CO2 and N2O concentrations of respectively 222 mg/L and 2 mg/L were measured. In the bottles with "pollina" we found, at different times of incubation, high concentrations of CO2 (highest value 25.2%), low levels of O2 (lowest value 0.5%) and negligible concentrations of N2O (< 0.015%).
All these findings suggest that the atmosphere inside the concrete well was altered by the fermentative processes of pollina. The death of the two workers, caused by a poorly oxygenated atmosphere with a high concentration of carbon dioxide, can be classified under the confined space hypoxic syndrome (CSHS).
二氧化碳（CO₂）是一种高密度气体，倾向于在大气的最低层分层。它可由中性地热排放、发酵过程或人类及工业活动产生。当二氧化碳浓度在密闭且通风不良的空间中升至非常高的水平时，缺氧危险是导致严重事故的一个非常重要的原因，可能涉及工人和救援人员。考虑到这种气体无味的特性，当二氧化碳水平高于20%时，发生致命事故的风险非常高。
描述了在检查一口混凝土井时发生的两起工人死亡事故，该井是农村地区污水管网的一部分。事故发生后的几周内，对井内气体的成分和浓度进行了分析。我们还考虑了在混凝土井周围地面上发现的一种名为“pollina”的有机肥料的影响，以确定发酵是否会改变井内的气体成分。
在井中采集空气和水样，并采集混凝土井周围地面上的有机肥料（pollina）样本。将不同数量的有机肥料（pollina）在有水或无水的情况下，置于密封玻璃瓶中，在20摄氏度的黑暗房间中培养；培养7天和18天后对玻璃瓶内的空气进行分析。所有空气和水样均通过气相色谱 - 质谱联用仪进行分析。
事故发生后2周、16周和18周在井内采集的空气样本分析显示，氧气浓度较低（范围为4.2 - 9%），二氧化碳浓度较高（范围为5.9 - 12.3%），氮气水平正常（范围为78 - 85%），一氧化二氮浓度在0.03%至0.19%之间。在事故发生后2周于混凝土井底采集的水样中，测得二氧化碳和一氧化二氮浓度分别为222毫克/升和2毫克/升。在装有“pollina”的瓶子中，在不同培养时间发现，二氧化碳浓度较高（最高值为2
