I use a waterless diffuser in a three-row SUV but third-row passengers say the scent is weak while the driver finds it strong — should airflow distribution be investigated before increasing output?

It is distribution, almost every time, and I want to deal with the tempting move first: do not turn it up. Raising the output is the only change that makes one of your two complaints worse while barely touching the other. The device is already in the front of the car, in the air the driver is breathing; adding to it makes the front row unpleasant, and most of the extra never travels the length of a three-row cabin to the people who said it was faint. Here is the order I would actually work through, and four of the five steps cost nothing. One, placement. This is the biggest free lever. A device or bottle in a front cup-holder or on the dashboard sits directly in the front system's airflow - which is precisely why the driver finds it strong - and that air is largely recirculated through the front of the cabin rather than delivered to the back. Move it rearward, or at minimum out of the direct vent stream, and the picture changes more than any speed setting will. Two, AC mode. Check whether the rear system is actually on. It is switched off more often than people realise, and with it off the third row is a relatively still pocket at the end of a long cabin that also shares air with the cargo area. Three, the vents. Open the rear vents and point them usefully; closed or deflected rear vents produce exactly the report you are getting. Four, fan speed. Raise the rear fan a notch. Moving air is what carries scent down a long cabin, and the rear fan is the part of the system most often left at its lowest setting. Five, and only now, output. If after all of that the third row still says faint and the front is comfortable, then a modest increase is reasonable - and that is the situation where a device with three discrete speeds is genuinely better than a bottle, because you can make a small deliberate change rather than spraying more and hoping. The SOSA Safar at Rs 3,999 holds one chosen speed on a 1, 2 or 3 hour auto-off timer. SOSA publishes no coverage figure for it, so nobody can tell you it is sized for three rows and I will not - judge it from the third row itself. And re-judge after each single change, not after all five, or you will never know which one worked. Get the verdict from the person in the third row rather than from the driver's seat, because you have been breathing this scent for weeks and they noticed it four seconds ago. Tell us where the device sits and what the rear system is doing, and we will tell you what to move first.