Ventilation keeps an underground mine breathable, but it is also one of the largest electricity loads on site. Many mines run fans at a fixed rate sized for the worst case, which means they spend energy moving air through areas where nobody is working.
Ventilation on demand (VOD) changes that. It adjusts airflow to match what the mine needs at the time. This guide explains how it works, what has to be in place for it to be safe, and how to judge the results.
What ventilation has to do
Underground ventilation supplies oxygen, dilutes and removes gases, diesel exhaust and dust, and controls heat. Ghana's L.I. 2182 regulation 179 requires adequate ventilation where people travel or work underground, with oxygen not less than 19% by volume, limits for carbon dioxide, carbon monoxide, sulphur dioxide, nitrogen dioxide, nitrous fumes and methane, and a minimum airflow for each person underground.
This is a plain-language summary for general information, not legal advice. Regulation numbers refer to L.I. 2182. Always check the current regulation text and Minerals Commission guidance for your operation.
How ventilation on demand works
A VOD system links sensors, fan drives and a control system. Instead of a fixed fan speed, it varies airflow against set-points and live conditions.
- Sensors measure airflow and atmospheric conditions at key points in the circuit.
- Variable-speed drives let fans slow down when demand is low and speed up when it rises.
- A control system applies the rules, for example airflow targets by area or shift pattern.
- A surface control room shows the state of the whole circuit.
Strata's StrataConnect VAC is an example of this approach, automating ventilation against predetermined variables and custom set-points.
The safeguards a VOD system needs
Saving energy must never compromise air quality. A sound design includes:
- Minimum airflow limits that the system can never go below.
- Continuous atmospheric monitoring, such as carbon monoxide in return airways as required by regulation 179(4), feeding the control loop.
- Alarms and automatic return to full ventilation if a reading goes out of range.
- Manual override and clear fail-safe behaviour if sensors or communications fail.
- Regular checks of air quantity, quality and speed by a competent person, which L.I. 2182 regulation 186(1) requires at intervals not exceeding three months.
Seals, stoppings and airflow control
Automation only works if air follows its intended route. Stoppings, overcasts and seals isolate worked-out areas and direct air to active workings. Leaky or damaged ventilation structures waste fan energy and starve the working faces. Products such as Strata's 3D Spray Panels are designed to seal off areas quickly, and they should be part of any ventilation upgrade.
How to measure whether it is working
- Energy: fan electricity use compared with a baseline before the project, adjusted for production.
- Air quality: time within limits for oxygen, carbon monoxide and other monitored gases.
- Reliability: alarms, overrides and sensor faults, and how quickly they were resolved.
Frequently asked questions
Is ventilation on demand safe?
Yes, when it is designed with minimum airflow limits, continuous monitoring, alarms and fail-safe behaviour, and when air quality is verified independently. The aim is to remove wasted airflow, not to reduce protection.
What does Ghana require for underground ventilation?
L.I. 2182 regulation 179 requires adequate ventilation, sets oxygen at not less than 19% by volume, sets limits for several gases, and requires continuous monitoring so carbon monoxide can be detected in main return airways. Check the current regulation text for the exact requirements.