Fainting, or "blacking out," has numerous causes. Sometimes the person "comes to" quickly (e.g., the cause is prolonged standing in heat), or the person won't respond (illness), and this kind of cause can be life threatening.

Signs someone's about to faint include frequent yawning, chest tightness, teetering, heart palpitations, nausea, a slow pulse, dizziness, lightheadedness, and sweaty, cool and/or pale skin.

At the onset of these signs, one should lie or sit, then place head between legs to increase blood flow to the brain. This should remedy the problem in many cases. But if someone faints and doesn't regain consciousness, it could mean a serious condition like heart attack, head injury, diabetic complication or a drug or alcohol overdose. Seek help for them in such cases.

Move the person to a cooler place if you suspect excessive heat. Lay them on their back, with legs elevated 8-12 inches. With a cool moist cloth, wipe their forehead. Loosen clothes and if possible, give them water with a teaspoon of salt, or a sports drink.

Tilt the head back and lift the chin to help air get through. Make sure they're breathing. If they aren't, call 9-1-1 and begin CPR. Roll victim on their side if they vomit. Check for injuries if the victim has fallen.

What never to do:

• Never try to get an unconscious person to swallow fluids.
• Never leave an unconscious person alone.
• Don't splash water on the victim; don't shake or slap.
• Don't put a pillow under their head.
• Don't move the victim unless it's absolutely necessary.

Call 9-1-1 for a fainted person if:

• There's no breathing
• They have diabetes
• They're bleeding or injured
• There's chest symptoms or a pounding or irregular pulse
• They're pregnant
• They're 50-plus
• There are stroke symptoms: slurred speech, numbness, paralysis, one-sided weakness, visual disturbances
• They haven't come to after two minutes

In the meantime, make sure the victim's airway is open, that they're breathing and have circulation (heartbeat). Check their body for medical information such as a bracelet.

Robert Siciliano personal and home security specialist to BestHomeSecurityCompanys.com discussing burglar proofing your home on Fox Boston. Disclosures.