# How to read map?

**URL:** <https://community.purpleair.com/t/how-to-read-map/7489>\
**Category:** Data\
**Created:** [December 10, 2023, 6:14pm UTC](https://community.purpleair.com/t/how-to-read-map/7489 "2023-12-10T18:14:55Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Manuel](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/manuel/32/4113_2.png) [@Manuel](https://community.purpleair.com/u/Manuel)\
**Post date:** [December 10, 2023, 6:14pm UTC](https://community.purpleair.com/t/how-to-read-map/7489/1 "2023-12-10T18:14:55Z")

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Hi,  
I am not familiar with reading any kind of air quality maps, and when I see values I do not know what they mean/indicate. For example, what are the _AV-14-987 A_ levels measuring? Is there a key somewhere that gives more information about what each of these things are, or may be indicating, or may be impacting (both health and environment)?

any help would be most welcome!

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**Author:** ![Josh\_PurpleAir](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/josh_purpleair/32/2842_2.png) [@Josh\_PurpleAir](https://community.purpleair.com/u/Josh_PurpleAir)\
**Post date:** [December 11, 2023, 4:31pm UTC](https://community.purpleair.com/t/how-to-read-map/7489/2 "2023-12-11T16:31:06Z")

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Hi @Manuel, in the following image, the data being shown is “US EPA PM2.5 AQI.” You can [select different data layers](https://community.purpleair.com/t/purpleair-map-guide/90#configuration-menu-4) to change which data you are looking at.

![image](https://us1.discourse-cdn.com/flex020/uploads/purpleair/original/2X/4/409400fe9934a364249b490104f35bb6bf504f88.png)

You can also see “Sandy - Bluff A”. The name of the sensor is “Sandy - Bluff” and “A” refers to the laser counter the blue line shows data for. This is because many PurpleAir sensors use two laser counters to conduct independent measurements, referred to as [channel A and channel B](https://community.purpleair.com/t/what-are-channel-a-and-channel-b/3643). “Sandy - Bluff B” is showing data for the other laser counter from the same device.

“Riverton A” and “Riverton B” are also present in the image. These are lines showing data from a second sensor. Further information is found in our article on [how to use the map graph](https://community.purpleair.com/t/how-to-use-the-map-graph/1122).

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**Author:** ![Bat](https://avatars.discourse-cdn.com/v4/letter/b/7ba0ec/32.png) [@Bat](https://community.purpleair.com/u/Bat)\
**Post date:** [April 26, 2024, 8:03pm UTC](https://community.purpleair.com/t/how-to-read-map/7489/3 "2024-04-26T20:03:22Z")

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Hi Josh. Thanks for the explanation.

We’re running into a case where the two channels are just not agreeing on values or one of the channels is reading 0. In cases like the latter, can we fetch the data from the other channel that is reading reasonable measurements or is that not advised? The problem is that we are getting a whopping 0 from a sensor that should be in 100s.