Blowing hot and cold over factory comfort
September 1st 2006 Maintaining a comfortable shop floor environment can increase productivity and reduce absenteeism so it pays to get the equipment selection right.
Bradley Smith of Colt International's Climate Control Division discusses the heating and ventilation options available for manufacturing plants.
If every factory were identical, then the optimum environmental scheme would have been identified long ago.
However, factories come in all shapes and sizes, their thermal characteristics differ, their manufacturing processes are distinctive, and perceptions of comfort vary between individuals on the shop floor.
The Workplace (Health, Safety and Welfare) regulations stipulate that reasonable working temperatures should be maintained in all places of work. A minimum temperature is set out in the regulations, but no maximum temperature.
However, the guidance states:
"An acceptable zone of thermal comfort for most people in the UK lies roughly between 13oC (56oF) and 30oC (86oF), with acceptable temperatures for more strenuous work activities concentrated towards the bottom end of the range, and more sedentary activities towards the higher end."
But temperature is not the only comfort consideration in factories.
Air quality also plays a part. Risks relating to dust and fumes in the workplace come under the Control of Substances Hazardous to Health (COSHH) regulations, which demand that a specific and detailed assessment is carried out involving enclosure, local extraction and, possibly, filtration.
There are essentially three ways to remove heat and contaminants from factories a natural or powered ventilation system or, rarely, air conditioning.
Natural ventilation is always the most economical option if it is practical. In a car, ventilation airflow is driven by the wind effect of the vehicle travelling through the air or, when the car is at rest, by warmed buoyant air passing out through the windows. These same mechanisms of wind and buoyancy pressure drive airflow through natural ventilation systems in buildings.
There is usually a demand for ventilation for contamination control in the winter months as well as in summer, and it is important that the heating system designer takes into account the additional heat losses caused by this.
The heating solution chosen depends on an accurate assessment of the building construction, levels of insulation, existing services and prevailing conditions.
The first step is a review of the level of heat emitted from furnaces, ancillary process plant, lighting systems and solar gain. This data is then used to calculate the heat load. This, plus the type and use of the building, will determine the amount of heating and ventilation required to achieve comfortable conditions.
Creating comfortable summer working conditions in factories requires ventilation systems that can clear excessive heat and airborne dust. The need to create an escape route for extreme amounts of waste heat demands the use of industrial strength natural ventilators.
The Colt Labyrinth ventilator is an example of the type of equipment designed to meet these requirements, as is the WCO natural ventilator, which has clear opening louvres and controllable side dampers. These dampers permit warm air to escape when the top louvres have been closed because of rain.
When considering the introduction of fresh air, a modular air handling system, such as Coltair, can heat and filter as required.
Direct fired heating is typically employed in factories because it is efficient (offering approximately 92 per cent efficiency compared with 75 to 80 per cent from indirect fired heating). It can also introduce fresh air (since direct fired units can be run with their burners switched off to permit the introduction of cool air into the building in the summer months).
If a building already has a ventilation system, then it might be worth considering radiant heating. This heats people rather than the air, making it especially efficient for heating in specific areas where air change rates are high (although care must be taken not to negate the effect of radiant heating with ventilation rates that are too high).
Airborne pollutants can have a serious impact on equipment life and maintenance. The British Standard for gas heating suggests that systems should be serviced annually. However, equipment installed in dirty environments and/or without filtration systems may require more frequent servicing.
I will end with the same message I started with a correctly selected and installed industrial heating and ventilation system will create a more comfortable working environment, but every factory is different so it pays to seek professional guidance to determine the specific requirements for individual facilities. | 
