Sewage pipelines are heavily polluted areas with a common risk of poor ventilation. Therefore, the first step is to open the manhole covers to allow fresh air to circulate inside the pipelines for a period of time. If natural ventilation is insufficient, high-power ventilation equipment must be used to pre-ventilate the pipelines for a certain duration.
In addition, workers operating underground must wear a safety rope around the waist for emergency rescue if necessary. When conditions permit, full sets of pollution-proof rubber clothing should be prepared to minimize hazards to workers. For operations in relatively deep manholes, gas masks are mandatory as a precaution against unforeseen risks.
For other cleaning tasks, the goal is to ensure the work is carried out in a timely, thorough, and clean manner without causing secondary environmental pollution.