This works well and it's been helpful to know what the air quality is furring this hazy summer of Canadian forest fire smoke. Easy to use.

It has an alarm. If particles exceed a value that you have set, it will wake you up. If you set it to a low value, it will alarm far sooner than a smoke detector will. If you are downwind from a wildfire, it will wake you. As for CO2, that gas builds fast in a closed house. It allows me to open the windows and run the fan for a short while even if outside temps aren't favorable so as to blow the gas out. However, with our central heat or A/C on, our house approaches outside conditions. I also have a VOC and formaldehyde meter. Not necessary unless you have specific VOC problems because when you air the house for CO2, you will also blow all the other gasses out. VOC meter have to be recalibrated occasionally. Particle and CO2 meters do not. NOW FOR THE DOWNSIDE. YOU NEED 2 PARTICLE METERS. They are cheap so they are not scientific instruments. Mine "goes off the ranch" occasionally and shows the particles being very high. Then it settles back down. But that will wake you with a false alarm. Another problem, when you have the alarm on for particles, CO2 does not appear on the screen. You would need 2 of these devices to set an alarm for particles and another device to set for CO2. So i will buy another just like it soon. High CO2 can make me kind of dementia like when i first wake up. Being outside when there is no pollution is the best thing for a clear mind. So, 4 stars with one meter. 5 stars with 2 meters. I read an article that you need 3 devices, but i am not going for 100% accuracy. Two will have to do on my budget.

It has an alarm. If particles exceed a value that you have set, it will wake you up. If you set it to a low value, it will alarm far sooner than a smoke detector will. If you are downwind from a wildfire, it will wake you. As for CO2, that gas builds fast in a closed house. It allows me to open the windows and run the fan for a short while even if outside temps aren't favorable so as to blow the gas out. However, with our central heat or A/C on, our house approaches outside conditions. I also have a VOC and formaldehyde meter. Not necessary unless you have specific VOC problems because when you air the house for CO2, you will also blow all the other gasses out. VOC meter have to be recalibrated occasionally. Particle and CO2 meters do not. NOW FOR THE DOWNSIDE. YOU NEED 2 PARTICLE METERS. They are cheap so they are not scientific instruments. Mine "goes off the ranch" occasionally and shows the particles being very high. Then it settles back down. But that will wake you with a false alarm. Another problem, when you have the alarm on for particles, CO2 does not appear on the screen. You would need 2 of these devices to set an alarm for particles and another device to set for CO2. So i will buy another just like it soon. High CO2 can make me kind of dementia like when i first wake up. Being outside when there is no pollution is the best thing for a clear mind. So, 4 stars with one meter. 5 stars with 2 meters. I read an article that you need 3 devices, but i am not going for 100% accuracy. Two will have to do on my budget.

I love this thing. I'm a professional Instrumentation Engineer and amateur mycologist. This is the best and funnest thing I've purchased in a long time. I just leave it plugged in and displaying all parameters all the time. I measure the amount of particulate coming out of my laminar flow hood, my fresh air filters, HEPA filters, etc. I measure CO2 levels in my tubs and in my clean room, humidity, temperature, etc. The measurement feedback is highly valuable and worth much more than the device. Love it.

I live in an area heavily affected by wildfire smoke. Our world is changing. I use it along with a cheaper indoor meter and air purifier to determine when I need to run the purifier. I've learned that my well insulated house holds in a lot of CO2 when the windows are closed... CO2 quickly quadruples. Particulate outside skyrockets with the the smoke. Great devices.