Where should a manual shutoff valve be installed in relation to all controls for vented wall furnaces?

A manual shutoff valve should be installed ahead of all controls for vented wall furnaces to ensure safe operation and accessibility. By positioning the shutoff valve in this manner, it allows for the immediate ability to stop the flow of fuel or air to the furnace in case of an emergency or maintenance requirement. This placement enhances safety since it enables users to turn off the furnace quickly without having to navigate through controls or other components that may be in the way. Proper placement of the shutoff valve is a key component in meeting safety regulations and ensuring that users can easily access the shutoff in a timely manner.