Hygienic assessment of artificial lighting
Artificial light is assessed by illuminance level (in lux) and flicker coefficient (in percentage). General illuminance is measured on a standard horizontal plane — 0.8 m from the floor.
Minimum lighting standards depend on the room's purpose:
- 150 lx: kitchens, bedrooms, living rooms;
- 200 lx: children's rooms;
- 300 lx: libraries, reading rooms, offices;
- 400 lx: stores, banks, post offices;
- 500 lx: classrooms.
Gas-discharge (fluorescent) lamps are excellent for spacious rooms and accurate color rendering, but are rarely used in households. At close range, they give the skin an unhealthy pale tint, and their design loses out to classical lampshades.
The problem of flicker and electronic control gear (ECG)
Incandescent lamps provide steady light, whereas gas-discharge lamps operating on alternating current create luminous flux fluctuations. This phenomenon is assessed by the flicker coefficient (Fc). Flicker has an extremely negative impact on vision, especially when working at a computer (according to SanPiN 2.2.2/2.4.1340-03, the Fc must be less than 5%).
To eliminate flickering, outdated electromagnetic control gear (EMCG) is replaced with electronic control gear (ECG). High voltage frequency stabilizes the discharge.
Advantages of ECG:
- electricity savings of up to 30%;
- absence of monotonous humming;
- extension of lamp lifespan by 30–50%;
- increased luminous efficacy;
- elimination of the need to regularly measure the Fc.
Classification of luminaires and local lighting
According to the direction of the light flux, lighting fixtures are divided into four groups. The most unfavorable are direct light luminaires (with an open bottom)—they blind with glowing incandescent filaments, create deep shadows, and fatigue the nervous system. Reflected light fixtures (light directed at the ceiling) are ideal for the eyes but require huge energy expenditures.
The golden mean is diffused or semi-reflected light (e.g., frosted globes or multi-tiered SK-300 fixtures). They protect the retina from direct radiation and evenly illuminate the space.
Rules of local lighting: Desk lamps and wall sconces are needed for localized brightness enhancement during reading. The main rule is to avoid sharp contrast between a bright desk and a dark room. When shifting gaze, the eyes must constantly readjust, causing rapid visual exhaustion. Combining local and general artificial lighting is completely safe for the eyes.
Ventilation and air exchange parameters
Indoor air quickly becomes polluted by excess heat, moisture, and metabolic gases from humans. Constantly breathing such air provokes headaches, decreased appetite, and worsens the course of pulmonary and cardiac pathologies.
Three basic criteria are used to maintain environmental purity:
- Air cube — the volume of space per person (standard 25–27 m³).
- Ventilation volume — the amount of fresh outdoor air per hour per person (standard 40 m³).
- Air exchange rate — how many times per hour the air is completely renewed (standard for residential housing is 1.5–2 times).
Natural ventilation (infiltration through cracks) provides only a 0.5–0.75 air exchange rate, which is insufficient. It is most effective to use tilt-and-turn transoms. They open inward at a 45° angle: the cold outdoor stream goes up to the ceiling, warms up, and smoothly descends without creating dangerous drafts.
Hygienic requirements for heating
The heating system must maintain a constant temperature without sharp fluctuations. For thermal comfort, the temperature difference from the floor to the ceiling must not exceed 2–2.5 °C per meter (otherwise, feet get cold, leading to colds, especially in preschoolers), and horizontally from the window to the inner wall — no more than 2 °C.
Important limit: the surface of radiators must not heat above 80 °C. When this threshold is exceeded, the process of dry sublimation of settled organic dust begins, causing unpleasant odors in the room and increasing the concentration of harmful substances. Traditional stove heating has serious drawbacks: daily temperature fluctuations reach 5–6 °C, and if the chimney damper is closed early, there is a high risk of carbon monoxide (CO) poisoning.
Briefly: answers to topical questions
Into which four groups are luminaires classified according to the direction of the luminous flux?
According to the direction of the luminous flux, luminaires are classified into four groups:
- Direct light luminaires.
- Reflected light luminaires — the majority of the luminous flux is directed at the ceiling, from where the light is reflected downward.
- Diffused or semi-reflected light luminaires — provide eye protection from bright light and distribute the luminous flux fairly evenly in all directions.
- Predominantly reflected light luminaires — these include the SK-300 luminaire with five metal shielding rings.
What types of mechanical (artificial) ventilation systems are used in residential and public buildings?
Local and central mechanical (artificial) ventilation systems are used in residential and public buildings.
- Local ventilation — services a single room, includes supply or exhaust electric fans, as well as modern air conditioning units.
- Central ventilation — provides air exchange throughout the entire building or in its main premises.
Depending on the purpose of the rooms, central ventilation is subdivided into:
- Supply — ensures the delivery of outdoor air.
- Exhaust — removes polluted air.
- Supply and exhaust — combines the supply of clean air with the removal of stale air.
Which diseases and pathological conditions are associated with sick building syndrome (indoor air-related illnesses)?
Sick building syndrome includes the following symptom complex in individuals living or working in such buildings:
- Headache and dizziness.
- Nausea.
- Irritation of the mucous membranes of the eyes and upper respiratory tract.
- Drowsiness and increased fatigue.
- Decreased performance.
In temporarily 'sick' buildings, including recently renovated buildings and new constructions, symptoms gradually lessen and completely disappear in about 6 months; in permanently 'sick' buildings, symptoms are observed for many years.
Direct light blinds, reflected light breaks the bank (energy consumption), diffused light protects and saves vision.
Class and exam questions
Why is it forbidden to use only a desk lamp in a dark room?
This creates a sharp contrast in illumination. Every time you look away from the desk, your eyes have to adapt to the darkness and back, leading to rapid visual fatigue.
How to properly ventilate a room in winter?
From a hygienic perspective, it is better to open windows fully for 5–10 minutes, repeating this frequently. With this regimen, the air is refreshed while the walls and furniture do not have time to cool down.
Why are electronic ballasts needed in lighting fixtures?
Electronic ballasts eliminate the flicker of discharge lamps, increase their service life by up to 50%, save energy, and operate without monotonous hum.
What else to study on this topic
- Organization of exhaust ventilation networks and in-wall ventilation ducts in buildings.
- Air conditioning systems: central and local, recirculation modes.
- Features of supply and exhaust ventilation in healthcare facility operating rooms.
- Classification of brick stove heat capacity and the risk of carbon monoxide poisoning.
Master the entire topic in the "Hygiene" course
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- Complete study guide on "Electromagnetic radiation in residential premises" and another 530 pages of the subject
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Other topics in the section "Chapter 4. Ecological and hygienic problems of populated areas and housing"
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.