# Filter by BoolMask

**URL:** <https://forum.dynamobim.com/t/filter-by-boolmask/53566>\
**Category:** Lists-Logic\
**Tags:** dynamo\
**Created:** [July 30, 2020, 10:29am UTC](https://forum.dynamobim.com/t/filter-by-boolmask/53566 "2020-07-30T10:29:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![zhelun.zhu](https://avatars.discourse-cdn.com/v4/letter/z/bc8723/32.png) [@zhelun.zhu](https://forum.dynamobim.com/u/zhelun.zhu)\
**Post date:** [July 30, 2020, 10:29am UTC](https://forum.dynamobim.com/t/filter-by-boolmask/53566/1 "2020-07-30T10:29:01Z")

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Hi everyone,  
I am having this problem with boolean musk.  
I fed the List.FilterbyBoolMusk node with a list of rooms and filter it with a musk coming from DoesIntersect node.  
The node works but the result is not correct. As you can see the DoesIntersect node has at least 1 true value in each list but the List.FilterbyBoolMusk gave back 3 empty lists.  
Can anybody tell me why?

 ![image](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/e/6/e656d1194c17c0e8aca924debc3f7c7f43dfaf06.png)

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<div class="post-metadata">

**Author:** ![Deniz\_Maral](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.dynamobim.com/deniz_maral/32/80323_2.png) [@Deniz\_Maral](https://forum.dynamobim.com/u/Deniz_Maral)\
**Post date:** [July 30, 2020, 11:08am UTC](https://forum.dynamobim.com/t/filter-by-boolmask/53566/2 "2020-07-30T11:08:47Z")

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List.Flatten after BoolMask and connect to element.