Date: 201809
Local time of day: 1801-2400
Location: BOI.Airport, ID
Flight conditions: Marginal
Weather elements / visibility: Haze / Smoke
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C BOI
ATC / advisory: TRACON BOI
Reporter organization: Air Carrier
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness; Time Pressure; Workload; Distraction
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed
Contributing factors: Airspace Structure; Human Factors; Procedure; Weather
Primary problem: Procedure

Narrative: After initial turn on for an approach to 28R Boise; ATC informed us that they had another aircraft turning on final and asked if we could see them; we replied no that we couldn't. The sun was sitting in the 10 to 11 o'clock position which made this difficult. Additionally there was a lot of haze from what we found out later was a controlled burn being done between us and the airport. We were at 6500 ft. and requested lower as the glide path was approaching. ATC would not give us lower as they were conducting Visual approaches. We requested the ILS approach and they would not clear us. We continued to try and spot the aircraft and the runway. We spotted the Runway and again pressed for a clearance. ATC finally asked if we could accept an approach to 28L and we replied that we could. At this point it was already questionable if we could get down and back on path by 1000 ft. I had the FO (First Officer) set in final flaps and initiated a descent. The FO stated that he wasn't sure that we had clearance and I leveled. We started cleaning up to discontinue the approach and ATC called realizing that we now were too close to conduct a normal approach and told us to come to heading 190 and to climb to 6500 ft. We had leveled at 6000 ft. We proceeded around the pattern and landed with no further issues.We decided to call the controller on the ground to get some clarity on what had happened on the approach. After talking to ATC they told me the controller should not have turned us to 190 until we were at 6500 ft.; as that was minimum vectoring altitude. This caused an alert. We told them that we would file to cover the event.ATC seemed to be preoccupied with the Aircraft turning in front of us. When we requested the ILS approach so that we could continue our approach; we got the response that they were conducting visuals and that wasn't an option. ATC wouldn't accept responsibility for the separation and conditions at the Airport and conditions were not in our favor for seeing the airplane or the runway at an extended distance. ATC seem unsure of what to do and we were going higher above the glide patch and were running out of time. At the last second they offered a side slip to runway 28L and we accepted; but at that point it was improbable that we would get down to a stable approach by 1000 ft. The time compression was very quick and events were happening fast. ATC decided to break us off of the approach and in doing so; it caused an altitude deviation for minimum vectoring altitude.We probably allowed the events to go on for too long without abandoning the attempt to get in. ATC was guilty of same problem. Events sometimes don't work out as anticipated and I am sure that Approach Control has reviewed how he handled the situation. The pilot monitoring (FO) did his job when he pointed out that in the confusion that he had not heard what I thought was a clearance. We discontinued the approach. ATC still in the accelerated time mode that had occurred tried to get us back around for another approach quickly and cleared us for a turn before he had established us at minimum vectoring altitude.


Second narrative: [Report narrative contained no additional information.]


Synopsis: A B737 flight crew reported descending for an approach prior to receiving clearance and then being vectored below the Minimum Vectoring Altitude by ATC.