Learn me interconnected smoke alarms and carbon monoxide detectors

I'm looking for advice on what to buy to protect me, my wife and two cats. I have a 2000 square foot ranch house, with three bedrooms and a 2000 square foot unfinished basement which includes the laundry. I have gas forced air heat and a gas dryer. The kitchen has an electric range. I also have a 10x19 enclosed sun porch with a hot tub in it that is closed off from the house by two exterior doors. And finally my two car garage is attached on the main living level but rarely has running cars in it. Don't judge me, it's a long term project car.

So how many should I have on each floor? Can I get a combo unit that is both smoke and carbon monoxide sensing? Has anyone ever made a decent unit for use in a kitchen that doesn't constantly go off from normal cooking? Should I put any into my attic/loft area?

Help me make a wise decision.

Very small knowledge, but just bought some for new to me campers maiden trip. 
Found out CO while technically heavier than "air" is not by much, and mixes well as it disperses. So, they recommend one within 5 ft of each source. 
There are two types of smoke detection: ionizing and photo cell.  Some can be bought with both. 
I bought (for low end pricing) a CO / photo cell smoke alarm for up high. A ionization smoke alarm  also for up high. And a CO / propane alarm for down low. 
That's my thoughts on the 18' camper, so your needs will be slightly different. 
That's just fresh in my mind!

Some quick guidelines:

- Install at least 1 on every level of your home

- Install 1 inside every sleeping area of the house

- Install 1 outside every sleeping area of the house

- Ionization units are for hot flaming fires. CO photocell are for smoldering ones. Dual units are best

- Interconnected AC  units should also have a battery backup

- Install 1 near other possible sources of ignition

- Install heat sensors instead of smoke detectors in kitchen 

- Install 1 near the top of all stairwells 

- I would install in garage.  Even if they are not running, they have fuel, and other flammable a are stored in garage

- Yes, there are combination smoke and CO2 units

- There are wireless interconnected units which are really easy to install in existing houses. 

- Install all units within 1' of the ceiling

- I wouldn't install in attics.  Too much dust and potential for false alarms

- You can also have third party monitoring of systems, but that is usually only for commercial spaces

Also, interconnected smoke detectors are the work of the devil.  In theory, I get it: no matter where you are in the house, you will hear the alarm and that's great.  But some of the systems have absolutely no way to discern which of the alarms is sourcing the signal and which are just repeating it.  So at 3am when one of them malfunctions, you're going to be running through the whole house trying to figure out if you have a fire, if you have a false alarm, and which room is either burning down or needs a new detector.

Whatever you buy, make sure that the interconnecting system has some way for each alarm to indicate if it is the source or a repeater.  I replaced all of ours a year or so ago and the new ones have an LED that lights up if it's the source of the alarm. 

They have some with a 10 year battery in it.  Since the smoke-sensing hardware has a useful life of about 10 years, it works out perfectly and you never have to change batteries.  I did one of those in the master bedroom because the smoke detector is so high up that I need a ladder.  That means that I never changed the battery in that one because I was going to get the ladder later on.  The rest can be changed while standing on the ground, so I went with regular 9v battery units for those.

In reply to SV reX :

Heat sensors are a better choice for garages.  Smoke detectors may be accidentally set off by car exhaust or dust raised when working on projects out there.

If there is a security system, smoke detectors and heat sensors should be connected to it for monitoring.

In reply to stuart in mn :

Good point

In reply to wae :

If your smoke alarm goes off at 3AM, running through the house trying to figure out if you have a fire is EXACTLY what you should be doing. 
 

There are lots of interconnected devices that indicate which device. A non-interconnected system is completely worthless. 

Does anyone have any specific recommendations for purchasing? 

wae said:

Also, interconnected smoke detectors are the work of the devil.  In theory, I get it: no matter where you are in the house, you will hear the alarm and that's great.  But some of the systems have absolutely no way to discern which of the alarms is sourcing the signal and which are just repeating it.  So at 3am when one of them malfunctions, you're going to be running through the whole house trying to figure out if you have a fire, if you have a false alarm, and which room is either burning down or needs a new detector.

Whatever you buy, make sure that the interconnecting system has some way for each alarm to indicate if it is the source or a repeater.  I replaced all of ours a year or so ago and the new ones have an LED that lights up if it's the source of the alarm. 

They have some with a 10 year battery in it.  Since the smoke-sensing hardware has a useful life of about 10 years, it works out perfectly and you never have to change batteries.  I did one of those in the master bedroom because the smoke detector is so high up that I need a ladder.  That means that I never changed the battery in that one because I was going to get the ladder later on.  The rest can be changed while standing on the ground, so I went with regular 9v battery units for those.

this, very very much this.  With 9' ceilings at 3AM this is what that looks like; your dogs are hiding in fear, your wife is mad that everybody is awake, and you're walking around the house with a step stool trying to unplug them all to figure out which one is going nuts.  

funny story: 
when i was a small child my grandfather was a member of the Chicago Fire department.  He asked me what you should do if a smoke detector starts going off.  I answered without missing a beat "put it outside"

SV reX said:

In reply to wae :

If your smoke alarm goes off at 3AM, running through the house trying to figure out if you have a fire is EXACTLY what you should be doing. 
 

There are lots of interconnected devices that indicate which device. A non-interconnected system is completely worthless. 

The ones we have send all alerts across the interconnection, so when a failure alert goes off; which is a different alert than a fire...