I think Jean and As Nur are talking about different things?
True that it is best to minimize variables (no additional smell other than the intended, red lights to remove any association with certain food, no perfume allowed, etc...) during a sensory evaluation training session.
But when you are in the Hospitality Industry, it is your job to create nice and comfortable environments to the customer, so they enjoy their stay. One of the ways as mentioned by Jean, is through the 5 senses.
BTW, Jean, I ever hear from a supplier that one of their customers use a paint, incorporated with fragrance cyclodextrin, and the smell of fragrance was released slowly from the freshly coated wall for up to a year... Interesting... Maybe you can get a similar paint product with fragrances, so you don't have to keep spraying air refreshener every now and then.