Workplaces of all kinds offices, shops, factories, hospitals or laboratories among others, require a standard of fresh air to ensure a healthy working environment. So it is important for any employer to be aware of the basic rules and standards of effective general ventilation.

The Health and Safety Executive provides information about this important issue on its website,

In addition, other publications provide useful information on the subject (here).

With this information, employers can ensure a compliant working environment and employees have access to information that might be able to understand the benefits and limitations of effective general ventilation at their work spaces.

General ventilation’ or ‘dilution ventilation’ is a term used to define the flow of air into and out of a working area, for example an office space, so that any contaminants are diluted by adding some fresh air. According to the HSE, this can be provided by:

a) ‘Natural ventilation’, which relies on wind pressure and temperature differences to move fresh air through a building and is usually not fully controllable; or

b) ‘Forced/mechanical ventilation’, which uses mechanical supply and/or extraction to provide fresh air and is controllable.

The basic guidelines for the general ventilation of a workplace, argue that all workplaces need an adequate supply of fresh air, and this can be achieved either by the natural ventilation from doors or windows or by air supplied or removed by a powered fan.

Usually, natural ventilation will normally be enough to control dusts and vapours from cleaning materials inside offices or shops. However, in other spaces, like workshops or fabrics, powered general ventilation could be needed.

In this cases, a Local Exhaust Ventilation (LEV) refers to an engineering control solution to reduce exposures to dust, mist, fume, vapour or gas in a workplace. This type of ventilation demands a proper design, so that the LEV system can draw dust, fume, gases or vapour through a hood or booth away from the worker.

An extraction system should be as well needed in these spaces, and it should effectively capture and contain the harmful substance before it is released into the working environment. In this sense, air should be filtered and discharged to a safe place.

According to HAS, a system like this should be robust enough to withstand the process and work environment, and also to be properly maintained and controlled, to ensure it is working effectively.

To apply extraction, we must not overestimate the effectiveness of small hoods, the hood is usually too far away from the process and does not surround the process enough. Also, we must be aware about inadequate airflow, and check often that the extraction continues to work.

The Health and Safety at Work (Act 1974, Section 2) requires that any employer provide and maintain a working environment that is, so far as is reasonably practicable, safe and without risk to health. This means that the employer actually undertake a risk assessment and prevent or control the exposure of his employees to substances hazardous to health by using suitable control measures which includes general ventilation, as well as a proper maintenance, examination and testing of the control measures.

It is important to provide the workers information about the proper conditions they should work under, as about the performance of the systems of ventilation and extraction that may have been installed. This is a clue to have them properly used and maintained.