History of Manholes
When underground sewer lines were originally built, engineers only provided for narrow holes to view the flow. However, workers needed to be able to get underground in order to be able to perform repairs. In addition, sewers need oxygen to prevent the growth of bacteria that leads to rotten egg smells. Therefore, manholes were designed and added to wastewater systems. Their covers provided for easy entry and exit. The perforations allowed for manhole ventiliation.
Need for Additional Ventilation
In the underground, confined space of the sewer, workers encounter reduced oxygen supply. They also are exposed to hydrogen sulfide, a sewage gas that negatively impacts health. Workers may complain of irritated eyes, difficulty breathing, and dizziness. In extreme cases, workers may die. Ventilation systems supply fresh air to the underground space.
Employers need to comply with OSHA regulations, including the Construction Confined Spaces Standard. The standards require testing of the air in confined spaces for oxygen levels, toxicity, and explosive potential. Carefully documented plans protect workers during the time that they spend underground.
Options in Equipment
Part of the worker protection strategy may involve the use of blowers and ventilation systems. They often consist of tube duct systems that travel into the manhole. Many popular options are portable, making it easy for workers to transport from place to place across a job site. They also usually collapse into a smaller package for easier storage. Some versions are made of recyclable materials for companies looking to reduce their carbon footprint. Blowers can provide heated air, if desired. If a ventilation system needs to extend for some distance down a tunnel, the tubing lengths may be connected to each other with duct to duct connectors.
Keeping workers breathing safely in sewer lines requires testing, monitoring of the air, ventilation, and protective equipment. The best options will be easy for workers to transport and deploy.