Short answer
A scent test in a real space must assess how the scent spreads, where it is noticeable, how the intensity evolves and whether the formula still suits the brand after longer exposure. So test with the final diffusion system and under normal conditions of use.
Don't start at maximum intensity
Start with a low setting and give the space time to build up a stable scent background. The setting can then be increased gradually.
A first test that is too intense distorts the assessment and can cause people to find the scent tiring more quickly.
Walk through the space
Don't just assess next to the device. Check the entrance, middle zone, corners, stairs, open doors and zones near ventilation grilles.
A space can have olfactory "hotspots" and quiet zones. That often says more about placement and air flows than about the strength of the perfume formula.
Test at different times
Ventilation and visitor flows change throughout the day. A shop with closed doors in the morning can have a lot of air exchange in the afternoon. A hotel lobby can have peak moments when doors open constantly.
So test at least under conditions that are representative of normal use.
Use people who have just walked in
Employees who have been present for hours are not an ideal reference because of olfactory habituation. Also ask people who have been outside for a few minutes to re-enter the space.
Assess three things separately
Technical performance: does the scent reach the right zones?
Comfort: is the intensity pleasant during a longer stay?
Brand fit: does the scent still feel right when it is part of the entire space?
Document the setting
Once the right balance has been found, record the programme, intensity, location and any seasonal adjustments. This way the scent experience can be reproduced later.
The space test is the real final
A blotter is excellent for comparing compositions. However, the brand scent is not used on paper. The final assessment should therefore take place in the environment for which the scent is intended.