UV-C Germicidal Lamps: 254 nm Dose and Exposure Limits

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The CDC/NIOSH guideline for upper-room ultraviolet germicidal irradiation (UVGI) explains that germicidal UV is generated by passing an electrical charge through low-pressure mercury vapour in glass tubes that transmit selected wavelengths, with an optimal germicidal wavelength of 254 nm in the UV-C range. It warns that lamps made for tanning emit UV-A or UV-B, that some lamps emit at 184.9 nm and produce ozone, hazardous even at low concentrations, and that low-pressure lamps should be rated for low or no ozone and contain only a small quantity of mercury (5 mg or less). The guideline notes that the design temperature range of 68–75 °F suits low-pressure mercury lamps and that upper-room effectiveness falls as humidity rises, recommending relative humidity of 60% or less. [1]

FDA's consumer guidance on UVC lamps adds that some UVC lamps generate ozone that can irritate the airway, that UVC can degrade plastics, polymers and dyed textiles, and that lamps containing mercury need extreme caution when broken and at disposal. [2]

Give the supplier the application (upper-room, in-duct, chamber, conveyor), lamp type and wavelength, UV-C output at rated conditions, ozone rating, mercury content, lamp length, base and driver, operating temperature and airflow, expected life and output decay, fixture shielding and interlocks, required dose or fluence at the target, and certifications for your market.

Keep people below exposure limits and dose the target

NIOSH gives the CDC/NIOSH recommended exposure limit at 254 nm as 6 mJ/cm² for an 8-hour shift (the same as the ACGIH TLV), corresponding to a maximum irradiance of 0.2 µW/cm² for 8 hours; upper-room designers have used 0.2 µW/cm² as the maximum in the occupied lower room. A well-designed upper-room system aims for an average fluence rate of 30–50 µW/cm² in the upper irradiated zone; for rooms with about 2.4 m (8 ft) ceilings it offers rules of thumb of 1.87 W/m² UV-C irradiance or 6 W/m³ UV-C power distribution in the upper zone. Air mixing matters: in a room without adequate mixing, effectiveness rose from 12% to 89% when a mixing fan was added. [1] FDA notes that UVC inactivates only organisms directly exposed, so dust or body fluids can shield them; that home lamps can be low-dose and need longer exposure; that in-duct use is the safest because it limits skin and eye exposure; and that improper installation in occupied rooms has caused skin and eye burns. [2]

Editorial calculation: 6 mJ/cm² is 6,000 µJ/cm², and at 0.2 µW/cm² that dose accrues in 6,000 / 0.2 = 30,000 s, about 8.3 hours, matching the 8-hour basis. For an upper zone of 20 m² floor area and 0.6 m depth (12 m³), the 6 W/m³ rule gives about 12 × 6 = 72 W of UV-C. Room area and zone depth are assumed examples; design should be done or checked by a qualified UVGI professional, as the guideline recommends.

Read the lamp data sheet: UV-C output, life and safety group

LEDVANCE's product data sheet for its UVC T8 30 W G13 germicidal lamp (2023) lists it for air purification, water purification and surface sterilisation, ozone-free, with a special coating for long life and high UV-C radiance at 254 nm. It classifies the lamp as photobiological Risk Group 3 (EN 62778; ANSI/IESNA RP-27.3-96) and warns that eyes and skin must not be exposed to direct or reflected UV and that the lamp is not for general lighting. [3]

Ask for UV-C watts (not electrical watts) and the life rating when comparing lamps, together with the safety group and ozone class; the exposure limits and upper-room design guidance above set how much of that UV-C may reach occupied space. [3] [1]

Editorial calculation: 12.6 W of UV-C from a 30 W lamp is a conversion of about 42%; at 10,800 h of nominal life, a lamp run 24 hours a day lasts about 450 days, about 15 months.

Rated output is not what an in-duct lamp delivers. A University of Alberta study measured 222 nm and 254 nm lamps in a 0.127 m × 0.127 m duct 1.16 m long: the 254 nm lamp's output rose by 18% as air temperature went from 25 °C to 35 °C and fell by 21% as air velocity rose from 0.5 to 2 m/s, while relative humidity of 25%–60% did not significantly affect either lamp. The 222 nm lamp was insensitive to air temperature and velocity; in E. coli efficacy tests with a life cycle analysis the authors found the 254 nm lamp more cost-effective and sustainable for continuous in-duct disinfection. Their spectrometer carried ±10% uncertainty at 254 nm. [4]

Editorial calculation: if a 254 nm lamp gave a UV-C output P at 0.5 m/s, the measured 21% drop leaves 0.79 P at 2 m/s, so a duct sized on catalogue output at still air would need about 1 / 0.79 ≈ 1.27 times the lamp output to hold the same irradiance at the higher velocity. [4]

UVC T8 30 W G13 (LEDVANCE)	Value
Radiated power 200–280 nm (UV-C)	12.6 W
Nominal lamp life	10,800 h
Nominal current / mains frequency	370 mA / 50–60 Hz
Starting time	30 s
Overall length / tube diameter	908.8 mm / 25.5 mm (T26), G13 base
Mercury content	3.0 mg
Ambient temperature range	+10 to +50 °C
Energy consumption	30 kWh per 1,000 h
Dimmable / burning position	No / any

State the application (upper-room, in-duct, chamber), required UV-C output and lamp length or base, and ask for UV-C watts at 254 nm, rated life and output at end of life, ozone class, mercury content and risk group.

Upper-room, in-duct and chamber uses, and the H-shaped quartz lamps a linked maker lists

Zhenjiang Jinxing, the linked maker, lists H-shaped quartz hot-cathode UV lamps; ask it for the UV-C watts, ozone class and mercury content of the model offered.

Applications include shielded upper-room fixtures suspended from ceilings or on walls, in-duct lamps for air disinfection, and enclosed chambers for surfaces. [1] [2]

UV-transmitting tube, mercury fill, electrodes and base, driver and fixture shielding

The tube row decides the ozone rating: NIOSH links ozone to lamps emitting at 184.9 nm, and an ozone-free tube blocks that line. [1]

Part	Role	Fix in the order
UV-transmitting tube	Passes selected wavelengths; blocks 184.9 nm if ozone-free. [1]	Glass type; ozone rating.
Mercury fill	Emits UV in low-pressure discharge. [1]	Mercury mass (≤ 5 mg guideline).
Electrodes and base	Connect to driver.	Base type; length.
Driver (ballast)	Powers the discharge.	Rating; dimming.
Fixture shielding	Directs UV away from occupants. [1]	Louvres; interlocks.

Wavelength, ozone, mercury, upper-room fluence, occupied-zone limit and in-duct output for a lamp order

The fluence, occupied-zone and environment rows are installation targets from the NIOSH guideline, not lamp ratings; lamp output comes from the data-sheet row and, in ducts, from the airflow row. [1] [3] [4]

Field	What it means and published values	Ask the supplier for
Wavelength	254 nm (UV-C) per NIOSH. [1]	Spectrum.
Ozone	Low or no ozone rating. [1] [2]	Ozone-free certification.
Mercury	5 mg or less (guideline). [1]	Mercury content; disposal.
Upper-room fluence	30–50 µW/cm² average. [1]	Fixture photometry.
Occupied-zone limit	0.2 µW/cm² (6 mJ/cm² per 8 h). [1]	Measured irradiance.
Environment	RH ≤ 60%; 68–75 °F suits lamps. [1]	Output vs temperature.
UV-C output and life	12.6 W UV-C and 10,800 h for one 30 W T8 lamp. [3]	UV-C watts; rated life; end-of-life output.
Duct air velocity and temperature	254 nm output fell 21% from 0.5 to 2 m/s and rose 18% from 25 to 35 °C in one duct study. [4]	Output at your air velocity and temperature.

Send the application, dose and safety data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Application: [upper-room; duct; chamber]
Lamp: [wavelength; UV-C output; ozone rating; mercury]
Dose: [target fluence or dose; exposure time]
Safety: [occupied-zone limit; shielding; interlocks]
Environment: [temperature; humidity; airflow]
Supply: [driver; life; replacement]

See manufacturer records Send an enquiry through CNFX

Buyer questions

What wavelength do germicidal lamps use?

NIOSH gives the optimal germicidal wavelength as 254 nm, produced by low-pressure mercury lamps. [1]

What UV exposure is safe for people?

The CDC/NIOSH limit at 254 nm is 6 mJ/cm² for an 8-hour shift, about 0.2 µW/cm² continuous. [1]

Do UV-C lamps produce ozone?

Some do; NIOSH says lamps emitting at 184.9 nm produce ozone and recommends lamps rated for low or no ozone. [1] [2]

How much UV-C does a 30 W germicidal tube produce?

LEDVANCE's data sheet for its UVC T8 30 W lamp gives 12.6 W of radiated power at 200–280 nm and a nominal life of 10,800 hours. [3]

Does airflow change a UV-C lamp's output in a duct?

In a University of Alberta duct test the 254 nm lamp's output fell 21% as air velocity rose from 0.5 to 2 m/s and rose 18% as air temperature went from 25 °C to 35 °C. [4]

Sources and what still needs a direct check

Sources checked 2026-10-12. The CDC/NIOSH upper-room UVGI guideline (2009) and FDA's UVC consumer guidance (2021 version) are US government documents, both cited from Internet Archive copies. LEDVANCE's data sheet covers one lamp model, and the University of Alberta duct study reports measured lamp output under airflow.

Still to check yourself

Choose wavelength and ozone rating.
Confirm mercury content and disposal.
Measure occupied-zone irradiance.
Check dose at the target.
Verify the legal supplier and factory.

UV-C germicidal lamp