CHIMNEYS
AVIATION OBSTRUCTION LIGHTS ON CHIMNEYS APPLICATIONS
A chimney is a typical cylindrical and vertical structure that provides ventilation for hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere.
In the special case of chimneys, cooling towers, and flare stacks lights may be displayed as low as 20 feet (6-m) below the top to avoid the obscuring effect of deposits and heat generally emitted.
BASIC RULES
- The number of light levels recommended depends on the height of the structure;
- The number and arrangement of light units at each level should be placed so the lighting is visible from every angle in azimuth;
- Lights are applied to display the general definition of an object or a group of buildings;
- The top obstruction lights should be placed sufficiently below the top so as to minimize contamination by smoke, etc
- The diameter of the structure determine the number of obstruction lights installed at the top and at each light level.

LIGHTS SPECIFICATIONS
- Low intensity lights should be used for structure with H ≤ 45 m during night time, if those are considered inadequate, than medium – high intensity lights should be used.
- Medium intensity lights type A,B or C should be used to lit extensive object (group of buildings or tree) or structure with 45 m < H ≤ 150 m.
- Note: Medium intensity lights, type A and C should be used alone, whereas medium intensity lights, Type B should be used either alone or in combination with LIOL-B.
- High intensity type A, should be used to indicate the presence of an object if its H > 150 m and an aeronautical study indicates such lights to be essential for the recognition of the object by day.
AVIATION OBSTRUCTION LIGHT MARKINGS
There is 3 option for lighting a chimney with aviation obstruction light systems.
- If the chimney is to be lighted only at night with red light
- If the authorities state that there is no need to light the day
- If the chimney marked with paint (white-red strip)
- If the chimney is to be lighted day and night with white light
- If the chimney is to be lighted with white light at daytime and with red light at night time
- If the authorities state that white light is too much discomfortable at night
1 – IF THE CHIMNEY IS TO BE LIGHTED ONLY AT NIGHT
HEIGHT | N° OF LEVELS |
H ≤ 45m | Only one level: Low intensity |
45m < H ≤ 105m |
2 levels:
Top level: Medium intensity – B Type; Intermediate level: Low / Medium intensity – B Type. |
105m < H ≤ 210m |
4 levels:
Top level: Medium intensity – B Type; First Intermediate level: Low / Medium intensity – B Type; Second Intermediate level: Medium intensity – B Type; Lower Intermediate level: Low / Medium intensity – B Type. |
Number of Levels According to Height

N° of lights depends on the diameter

2 – IF THE CHIMNEY IS TO BE LIGHTED DAY AND NIGHT WITH WHITE LIGHTS
Number of Levels According to Height

HEIGHT | N° OF LEVELS |
H ≤ 105m | Only one level: Medium intensity – A Type |
105m < H ≤ 210m |
2 levels:
Top level: Medium intensity – A Type; Intermediate level: Medium intensity – A Type. |
210m < H ≤ 315m |
3 levels:
Top level: Medium intensity – A Type; Intermediate level: Medium intensity – A Type; Lower Intermediate level: Medium intensity – A Type. |
3 – IF THE CHIMNEY IS TO BE LIGHTED WITH WHITE AND RED LIGHTS
HEIGHT | N° OF LEVELS |
H ≤ 105m |
2 levels:
Top level: Medium intensity – AB Type; Intermediate level: Low / Medium intensity – B type. |
105m < H ≤ 210m |
4 levels:
Top level: Medium intensity – AB Type; First Intermediate level: Low / Medium intensity – B Type; Second Intermediate level: Medium intensity – AB Type; Lower Intermediate level: Low / Medium intensity – B Type; |
Number of Levels According to Height
