In two separate incidents, the victims had set up barbecue grills inside their homes to stay warm.
Firefighters were first called to an apartment complex on Skyline Drive near Unity around 11:45 p.m. Wednesday.
Officials say a family of four, including three children, was using a pot with charcoal inside to try to heat up their home.
A neighbor ABC13 spoke with says the power came back on Thursday morning, but it feels like 22 degrees inside their units.
RELATED: 'We tried our best to save them,' said family of woman and 7-year-old who died from carbon monoxide poisoning
Less than an hour later, three children and three adults were taken to the hospital after a similar carbon monoxide incident in southwest Houston.
This time, firefighters were called to an apartment on Hodges Street.
Once again, officials say they were using a barbecue grill inside their unit to stay warm.
So far, it appears all six people will be okay.
Investigators say the leading causes of carbon monoxide poisoning are furnaces, stoves, fireplaces, water heaters, grills and running engines.
Carbon monoxide (CO) is a colorless, odorless, tasteless gas that is dangerous and potentially poisonous if inhaled. Here are some tips to protect everyone in your building from potentially deadly CO poisoning.
Mild exposure to CO can cause:
- Slight headache
- Blurred vision
- Flu-like symptoms that disappear when the person breathes fresh air
Medium exposure can cause:
- Severe headache
- Rapid heart rate
- Cardiac/respiratory arrest
Treatment for CO exposure is fresh air or oxygen. Severe exposure requires medical attention.
If you suspect CO is present in your building:
- Open windows to ventilate the area.
- Shut off your furnace and other fuel-burning appliances.
- If you're experiencing physical symptoms, get everyone, including pets, out of your building.
- If you have an attached garage, open the largest garage door.
- If you suspect problems with your appliances, call your gas appliance dealer or CenterPoint Energy's Customer Service.
- If CO is discovered, don't return to your building until the source is found and the problem corrected.
- Get to fresh air and call 911.
SEE ALSO: Family of 6 used charcoal grill for 4 hours to keep warm inside Cy-Fair area apartment
Houston hospital says it has treated 60 patients for carbon monoxide poisoning