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It would also nice to have it in a 12 volt relay form for my 12 volt system in my trailer.
As Steve pointed out, finding a sensor is the first step.
Then you have to make the critical decision, where are you going to set the alarm limit? If you do a web search, you will find all the dirt on setting CO level alarms. When the first home CO detectors came on the market in the USA, the alarm limit was set per the then current OSHA limit. That turned out to be too low and there were a lot of false calls to the fire department because the level of CO could normally and transiently be present and supposedly it was not a big deal.
Eventually a new standard was created and the alarm threshold was increased SIGNIFICANTLY. There are a lot of people that feel that the new limit is too high and unsafe.
So if you use a sensor out of a standard home CO alarm and use its output to turn on a fan instead of a buzzer, you are likely already in trouble and just turning on a vent is not going to help. If you go with a sensor with an analog output, one that you can use to alarm at a lower level, the design gets very complicated. If you use the sensor to turn on a fan, that is OK. But if you use it to sound an alarm, you may run afoul of the fire code which now mandates that a CO detector must NOT alarm at levels below a certain threshold.
---55p
Then you have to make the critical decision, where are you going to set the alarm limit? If you do a web search, you will find all the dirt on setting CO level alarms. When the first home CO detectors came on the market in the USA, the alarm limit was set per the then current OSHA limit. That turned out to be too low and there were a lot of false calls to the fire department because the level of CO could normally and transiently be present and supposedly it was not a big deal.
Eventually a new standard was created and the alarm threshold was increased SIGNIFICANTLY. There are a lot of people that feel that the new limit is too high and unsafe.
So if you use a sensor out of a standard home CO alarm and use its output to turn on a fan instead of a buzzer, you are likely already in trouble and just turning on a vent is not going to help. If you go with a sensor with an analog output, one that you can use to alarm at a lower level, the design gets very complicated. If you use the sensor to turn on a fan, that is OK. But if you use it to sound an alarm, you may run afoul of the fire code which now mandates that a CO detector must NOT alarm at levels below a certain threshold.
---55p
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So your saying the alarm is set to a point where a fan would be non effective to ventilate area. AND to set the level it needs to ventilate would be below what fire code regulation's? I think the big thing would be if it can be done can it be done with a home CO detector via relays and such?
Let me say it again:
If you use the output of a standard home CO detector available in the USA to turn on a fan (instead of a buzzer) to ventilate an area, you MAY be too late.
If you build you own detector using a raw sensor, you can set the threshold at which the FAN starts to be lower, which i think MAY be necessary for your safety. But if you use the same threshold to turn on an alarm as well, you MAY run afoul of the national fire code.
You need to do a bunch of research on CO levels, which will dictate what sensor you need to get.
---55p
Ok I understand about the threshold being to late (with standard CO detector) to ventilate to any effect. What I need to do is find information on what levels of CO would be good level to turn vent on . Now off to find a co sensor and to build it..I know Ill be back ..
Thank you all for your help you all saved me some trial and error time.
Thank you all for your help you all saved me some trial and error time.
I have strong opinions on this, but I am not going to stick my neck out and tell you what level you should be setting the threshold to.
Some US sources you can look for your research is OSHA and National Fire Code (I do not remember the formal name). The SAE (Society of Automotive Engineers) most probably has its own guidelines for acceptable levels in automobiles. Then there are customer advocacy groups and some internet nuts who will advocate much different levels, which may or may not be rooted in reality.
One other angle that you have to consider is the likely source of CO. Why is it being generated in the first place and how quickly it can accumulate? A vent fan like this should be for emergency use, to be followed immediately by having the problem fixed. Its use should not be part of normal course of business.
Do come back when you have more questions.
---55p
Some US sources you can look for your research is OSHA and National Fire Code (I do not remember the formal name). The SAE (Society of Automotive Engineers) most probably has its own guidelines for acceptable levels in automobiles. Then there are customer advocacy groups and some internet nuts who will advocate much different levels, which may or may not be rooted in reality.
One other angle that you have to consider is the likely source of CO. Why is it being generated in the first place and how quickly it can accumulate? A vent fan like this should be for emergency use, to be followed immediately by having the problem fixed. Its use should not be part of normal course of business.
Do come back when you have more questions.
---55p
