Lighting
Haze vs Fog
Definition
Haze and fog are two ways of making the air visible so that beams of light show. Haze consists of fine particles held in suspension and released continuously by a hazer; it is barely visible to the eye but reveals the beams, especially in backlight. Fog is a dense, clearly visible cloud, usually released in bursts. Low fog, produced with liquid CO₂, liquid nitrogen or a chilled fog machine, stays close to the ground and dissipates quickly.
In the field
Optical (photoelectric) smoke detectors can be triggered by dense haze. In a venue fitted with them, haze levels and timing are agreed with the venue's technical team, and any isolation or covering of detectors is approved in advance by the venue management under its fire safety procedures.
Related lessons
Sources
- ANSI E1.23-2020 (ESTA), Theatrical fog effects : planification des effets de fumée, dont la prévention des fausses alarmes de détection incendie · blog.ansi.org
- Wikipédia (pointeur secondaire), Fog machine : fumée, brume, fumée lourde (CO₂, azote, machines refroidies) · en.wikipedia.org