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By Evan Williams, Cambridge Companies

January 31, 2019

Safety, code compliance and cost effectiveness should all be central considerations when upgrading a facility.

Converting a fleet to compressed natural gas (CNG) can make a lot of sense to reduce fuel costs. Typical considerations toward making this decision include the cost of the new vehicles as well as the fueling infrastructure. An often-overlooked component, that is essential for a fleet CNG conversion, is the cost to modify the existing shop facility to ensure those new vehicles can be serviced in a safe and code compliant environment. It is essential to understand the activities that occur in the shop as they have a direct impact on the CNG retrofit building modifications.

Existing Shop Typical Improvements

As the existing shop is assessed, the first question should be about what might be required for it to be CNG compliant. While a qualified engineer or specialty consultant should be engaged to perform the detailed analysis and scoping, there are several elements that will likely need to be provided, as well as several items to avoid.


The existing ventilation system will likely need to be upgraded to afford more air changes per hour. The shop (if it is heated) is likely heated with a gas-fired unit or radiant tube heaters. These are typically not compatible with a CNG shop and will need replacement.

Shop Height

The height of the shop has a direct impact on the ventilation requirements. If the shop is shorter than 20′-0″, it may not be entirely viable for a CNG retrofit.

Gas Detection

It is likely that the existing facility does not have a gas detection system. One may be required by the local Authority Having Jurisdiction (AHJ).

Fire Separation

The walls that separate the shop from the administration offices will be required to be two-hour rated for a CNG Shop. If the current walls are not rated, upgrading these can be costly and disruptive to operations.


Look up at the ceiling and down at the floor. If there is any wiring or conduit in the areas within 18″ of the roof or the floor, it will need to be upgraded to Class 1, Division 2 rated.

This is not an exhaustive list of where all changes need to be made, but it is meant to help illustrate how the CNG retrofit work can impact many different areas of the shop. With a better understanding of areas where upgrades will likely be necessary, the next step will be to work with a consultant to perform a detailed analysis of the facility to better define which of the potential upgrades the facility will need to begin servicing CNG vehicles.

Read the full article on Waste Advantage Magazine