Sun protection for outdoor work: SPF 30 or 50?

What the sun protection factor tells you

The sun protection factor (SPF) describes how well a product protects against UVB radiation, measured in a laboratory with a standardised and fairly thick layer. Under those conditions, SPF 30 blocks around 97 percent of UVB and SPF 50 around 98 percent. The gap looks small, but it means roughly a third less radiation reaches the skin with 50 than with 30.

At work, people almost always apply less than in the lab, and sweat and friction wear the layer away. Real protection is therefore usually well below the printed value. That is exactly why a higher factor gives useful headroom during long shifts outdoors.

Check for UVA too

SPF refers to UVB. Also look for a UVA symbol on the pack, because UVA penetrates deeper into the skin and passes through clouds and window glass.

When 30 is enough and when 50 is better

Situation	Recommendation	Reason
Short outdoor tasks, mostly in the shade	SPF 30 may be enough	Limited exposure, provided it is reapplied consistently
All-day work on open ground	SPF 50	Long exposure; sweat and wind reduce protection
Roofs, facades, light surfaces, water, metal, snow	SPF 50	Reflection increases exposure, often more than expected
Cleaning with frequent switches between indoors and outdoors	SPF 50	Reapplication is easily forgotten during interruptions
Work at altitude or in the mountains	SPF 50	UV intensity rises with altitude

For most businesses in construction, landscaping or building cleaning, SPF 50 is therefore the pragmatic standard from spring to autumn. A single product simplifies purchasing, storage and instruction and avoids debates within the team.

Applying and reapplying during the working day

A high factor is of little use if it is only applied once in the morning. Sun protection only works with a routine that fits shifts and breaks.

Apply generously before starting, including ears, neck, bridge of the nose and backs of the hands.
Reapply roughly every two hours, at the latest at each break and after heavy sweating.
Reapplying does not extend protection time; it only maintains protection.
Water-resistant or sport formulas stay on better when you sweat.
Keep a lip balm with sun protection to hand.

SPF 30 reapplied consistently protects better than SPF 50 applied in the morning and then forgotten.

More than sunscreen: the order of measures

Occupational safety follows the sequence technical before organisational before personal, often referred to in Switzerland as the STOP principle. Sunscreen is the last level and supplements the other measures rather than replacing them.

Level	Examples
Technical	Shade sails, umbrellas and shading at fixed workstations
Organisational	Schedule strenuous work for the morning, breaks in the shade, rotation for exposed tasks
Personal	Long-sleeved, tightly woven clothing, helmet with neck flap or brimmed cap, sunglasses, sunscreen

In Switzerland, employers are required to protect their employees' health with appropriate measures. Suva, the Swiss accident insurance institution, publishes information material on working in the sun. For industry-specific questions, involve your safety specialist.

Setting rules for your business

Classify work sites by UV exposure: duration, shade, reflective surfaces.
Define a standard, when in doubt SPF 50 with UVA protection, and buy it centrally.
Keep sunscreen where the work happens: in the vehicle, the site hut, the cleaning trolley.
Link reapplication to fixed moments such as the morning break, lunch and the afternoon break.
Issue clothing and headwear as part of the equipment.
Brief new and temporary staff when they start.

Acceptance is the bottleneck

Products that feel sticky, sting the eyes or leave white marks on dark workwear are quickly dropped by the team. Test two or three products with employees before settling on a standard.

Frequently asked questions

Is SPF 30 enough for a full day outdoors?

Only with low UV exposure, plenty of shade and consistent reapplication. For a full day in open sun, SPF 50 is the more reliable choice.

Do I need sun protection when it is cloudy?

Yes. A large share of UV radiation passes through light cloud. Go by the UV index from the weather service rather than by how warm it feels.

Is SPF 50 automatically the better solution?

Not automatically. The factor offers more headroom but only works if enough is applied and it is reapplied regularly. The rule the team actually follows is what counts.

Do light surfaces really make a difference?

Yes. Light surfaces, glass, metal, water and snow reflect UV radiation and increase exposure, including on skin that would otherwise be in shade.

Who pays for sun protection?

Protective measures required by the work are, in principle, the employer's responsibility. Clarify details with your safety specialist or industry association.

Employees who notice skin changes that evolve or do not heal should see a doctor.