呼吸干净空气分两步：第一步，先得有一个净化器。第二步，知道怎么才能最好地使用它。我们列出了净化器的最佳使用方法—源于数据，无关直觉。
1. 记录购买日期
HEPA滤网是有使用寿命的。最好的判断更换滤网的根据是使用时长。我刚开始测试净化器的时候还以为可以根据HEPA的颜色来判断什么时候需要更换，可是数据表明HEPA在变黑以后很长时间里也还是可以维持净化效果的。在决定何时更换滤网这件事上，通过颜色判定并不靠谱。
虽然我们推荐的方法也不是特别精确，但至少容易操作并且有数据支持：记录你的HEPA初次开始使用的日期，然后在达到相应的使用时间以后更换你的滤网。
上图的计算是假设净化器每天运转8小时，你可以自己根据每天使用的时间和使用的天数来计算具体的需要更换滤网的时间。
2. 保证你的屋子密封良好
一个提高空气净化器效率的办法是确保你的房间密封良好。那最好的确保你的屋子密封良好的办法是使用密封胶带把门窗的缝隙都封一下。
密封良好的屋子的缺点
不过，密封屋子也要付出代价。房间密封性越好，我们呼出的二氧化碳就越容易累积。如果屋里人不多这也不是什么大问题，但如果屋子里有好几个人，二氧化碳就有可能达到较高浓度让人觉得头晕眼花。
其他室内的污染物也会积累。比如新家具或者新地板产生的甲醛。Smart Air的实际环境测试表明活性炭可以减少甲醛和其他有毒有害气体。
如果你想呼吸新鲜空气，我们的实验还发现就算你开窗通风空气净化器也还是可以进行空气的清洁。当然，开着一扇窗户或者在一个密封不好的屋里，你需要一个更强力的净化器并且需要更经常的更换HEPA滤网。
3. 空气净化器放在哪里好呢？
很多人为了方便和美观把空气净化器贴墙放置。
可是这样的放置位置对净化效果有什么影响呢？
为了让净化器达到最好的净化效果，就需要有一定的空间让空气净入净化器并且使干净空气释放到整个房间。如果让它背靠墙站着，就没有足够的空气来吸入脏的空气了。
那净化器需要离开墙壁多远呢？我决定用我们家的净化器来做个实验。
试验方法
我给大胖，小胖还有大炮分别做了测试。当净化器紧贴墙壁“罚站”的时候，空气吸入率只有5%！净化器离开墙壁4厘米的时候，气流就上升了94%。离开墙壁10厘米远（差不多是一个鼠标那么大的距离），气流就恢复到100%
结论：为了达到最好的净化效果，你需要把净化器放到离开墙壁至少10厘米。不过即便只是4厘米的空隙也会给净化器几乎最好的净化表现。
4. 你不用24小时开着净化器
有的净化器公司建议即便你不在家，也要24小时开机。
Smart Air的真实环境测试发现像大炮这样的DIY净化器可以在20分钟以内把北京一个13.5平米的房间污染物颗粒减低到20%。这就意味着你不在家的时候不用浪费能源或者你的HEPA寿命。
我可以在晚上关掉净化器吗？
跟上面那个结论完全相反，晚上你的净化器得开着。有的人有错觉，净化器净化了空气以后就可以给关上了，只要门窗关好，屋子里整晚的空气都没问题。但是，我们在北京真实环境的公寓房间里做了测试，关掉净化器看空气过多久就又脏了。
数据显示在短短15分钟的时间里污染物颗粒水平就回到了使用净化器以前的50%，80分钟以后就完全恢复到原始水平了。所以我们需要整晚开着净化器。（此外：这也是为什么小米那种内置自动模式经常会让空气在不安全的水平。）
Hi im wondering why the particulate levels still go up at night when the doors and windows are closed. Where are the particulates coming from?? Just so I can be more aware of where pollutants are coming from. Also want to thank you for doing all these tests and providing consumers like us with genuine and educational information. It has been a big help!
Great question, Gloria! The graph above in Tip number 4 refers to what happens when you turn off your purifier. After turning off the air purifier, outdoor PM2.5 starts to return back into the room (through cracks in the doors or round poorly-sealed windows. This then leads to an increase in indoor PM2.5
If you want to learn more about what time of day is most polluted, you can read our article on when pollution is lowest and highest during the day.
i hv hitachi epa 6000 which blows out clean air from top. it sucks from side gaps left and right. i placed the air purifier on the shelf. there is a gap of 20 cm from top of the air blower inbetween the ceiling. is that ok?
Hi Alex, we’ve never tested the model you are using. I think the best way is to spare it as much space as possible both for air inlet and air outlet. If you don’t have enough space for it, the best way to tell the threshold, if you have a budget, is to get an air quality monitor and see how well it works.
Does the hight placement of the filter have any effect on purification? Am I correct in thinking that there is more pollution closer to the ground, or does the action of the fan change all this if using, for example, the Squair in a 20m2 room?
Hi Simon, good question! In fact the air quality within a room, closer to the ground or the ceiling, doesn’t have a difference. Even living in a high rise building wouldn’t not make an obvious difference of the air quality: https://smartairfilters.com/en/blog/would-higher-floors-protect-us-from-pm2-5/ All of the tests we did are real room test in a Beijing apartment. So if the air monitor shows clean, it means the whole space is cleaned. For example, using a Sqair in a 20 sqm room, you will see the air quality monitor shows the same PM2.5 number close to the air purifier or farther away across the room.
Hi – i see that i can easily clean the Blast and Blast mini when the cover is taken off but may i ask if i should clean the Blast mini air inlet and also where the fan blades are? will that require cleaning and is it easy to do so?
Hey Angie! The pre-filter for the Blast and Blast Mini is on the back. It’s the black, mesh-like filter. This can be removed and washed with water and then left to dry. We recommend you do this every 2-4 weeks depending on how often you use your purifier! You can find more information in the Blast and Blast Mini manuals.
When to change air filter must be depending on particle mass/ volume air and amount of air pressed thru the filter.
1. I run my filter during a relatively clean period on max for 1 h , thereafter on min rest of the night.
2. I run my filter during heavy polluted times on max for 2 h, thereafter on medium rest of the night to handle the outside air seeping in.
The filter load is obviously not the same and to set a lifespan of 140 hrs is, in my mind, not correct.
My intention is to use a particle meter on both sides of the filter. From these parameters it should be possible to work out a point when filter needs changing. The meter sold by Smart Air equals the cost of 4 filters and I know, don’t guess.
I live in Malaysia with at times heavy pollution from burning rain forest for palm oil plantation, at other times air is in the green zone (below 50). I also never buy palm oil.