Pura is a smart home fragrance company, and the idea is simple. A plug-in diffuser holds a small vial of scent, and an app lets you set the intensity and schedule. Perfumer & Flavorist dates the company to 2015, though other listings say 2014, so I will just say about a decade ago. In that interview, CEO Bruno Lima credits his co-founder, Richie Stapler, with originating the idea of smart home fragrance. He says they spent about three years on ideation and beta devices before launch. The name is Latin for pure, and the company says its fragrances are paraben and phthalate free and cruelty free.

For pura fragrance, the draw is the vial system. You are not buying a candle you have to finish, you are swapping scents the way you would change a playlist. The brand has also worked with partners including Nest and Capri Blue, and it describes a marketplace of 300 plus scents.

The first grid is Pura, with three diffusers and five vials. The second grid is candles, room sprays and reed diffusers, for the people who prefer scent without a plug or an app to open. My tip: put a diffuser where air moves, like a hallway, and not right next to your bed.

Three devices first. The Pura Home Smart Fragrance Diffuser is the current main model, with app control and faster diffusion than earlier versions, and it comes with a one-year limited warranty. The Pura Home Mini Smart Fragrance Diffuser is an ultra-compact single-vial diffuser for small spaces, which suits a bathroom or a desk. The Pura Car Smart Fragrance Diffuser is cordless, runs about 15 hours per charge and recharges by USB-C.

Then the vials, which I would pick by mood. Pura Capri Blue Smart Vial Volcano is the partner scent, bright and citrusy, and it is the one to choose if you want a room to feel awake. Pura Smart Vial White Tea is a clean white tea scent that stays quiet in the background, which suits an office or a bathroom. Pura Smart Vial Cozy Cashmere is warm, soft and comforting, which is how I would describe the scent for a living room in November.

The last two are designed with partners. Pura Santal & Ginger is a woody blend designed with Studio McGee, and Pura Rainwater Lily has notes of rain, lily and florals for a clean, crisp scent. Each one is a single 0.33 fl oz (10 mL) vial, so they are easy to try in rotation.

What I would skip: running a strong scent in a small, closed room all day. Lower the intensity in the app, or use the Mini instead of the full-size device.

If you want scent without a plug, here is the comparison. VOLUSPA Santal Vanille is an 18 oz glass jar candle with santal, French bourbon vanilla and oud, and it burns for up to 140 hours. VOLUSPA French Cade & Lavender is earthier, with cade wood, verbena and Bulgarian lavender, and I would put it in a bedroom. NEST New York Sunlit Yuzu & Neroli is bright, with yuzu, mandarin and neroli, and Himalayan Salt & Rosewater is a softer candle with rosewater, geranium and salted amber.

Room sprays are the quick option. Diptyque Baies is the brand's best-known scent, blackcurrant leaves and Bulgarian rose. Aesop Istros Aromatique Room Spray is the quieter, design-led one. Spray either one a little away from the couch, not onto fabric, and start with a single pass because both are made to be noticed lightly.

Reed diffusers are the slow burn. Jo Malone London Wood Sage & Sea Salt Reed Diffuser is crisp, mineral and woody, lasting three to four months. NEST New York Grapefruit Reed Diffuser has pink pomelo, grapefruit and watery green notes and lasts approximately 90 days. Both work without electricity, and you flip the reeds over when you want a little more scent. They will never be as strong as a smart diffuser, and that is the point for a quiet room.

What I would skip: the heavy santal candle in a small room with no ventilation. It is a sweet, warm scent, and it builds fast.

I think the real reason to choose a diffuser is control. You decide how strong the room smells and when it stops, and you can change the vial when the mood changes. If you are not sure about a plug, start with the Mini and one vial in a scent you already like. Then, if you miss the flicker of a flame, go back to a candle for evenings. Most homes end up with both. If you want to keep browsing, I also put together YSL Myself Is Spelled MYSLF and Perfume And Fragrance Oils.