Safety Moment #25: Noise Limits

Noise boundaries on process and energy facilities

The material shown here has been extracted from the ebook 52 Process Safety Moments and in the book Plant Design and Operations.

Noise Limits


Exposure to high levels of noise is one of the most pervasive health issues on process and energy facilities. Therefore, it is important to define the maximum level of noise that is allowed in various situations.

There are many regulations and engineering standards to do with noise control. Some additional discussion and guidance to do with noise limits is provided in this Safety Moment.

Types of Operation

It is necessary to define the work areas that are covered. One company states that a work area is any position in which a person may be present and which is no less than 1 meter from equipment surfaces, or any position where a worker's ear may be exposed to noise in the normal course of his duty. It includes platforms, walkways and ladders.

Noise Control Barriers

The use of noise control barriers is shown in the sketch.

Noise Control Barriers
Noise Control Barriers

Types of Operation

Many facilities have noise limits for four types of operation:

  • Normal operations;
  • Special operations;
  • Intermittent or fluctuating noise; and
  • Emergencies.

Normal Operations

For normal operations the sound level to which workers are exposed should not exceed 85 dB(A).

Noise limits may differ for different times of day or night and for work-days or week-ends, particularly if the facility is located in a built-up neighborhood.

Special Operations

Examples of special operations are start-up, shutdown, regeneration and maintenance. At these times, and in properly defined and restricted areas, sound pressure levels above 85 dB(A) — but always below 115 — are allowed. To meet this target some equipment may have to be confined in a protective enclosure. Alternatively, personnel may wear appropriate hearing protection. Signs that follow the guidance provided in ISO 3864 should be provided.

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