CIH - Ventilation
Ventilation Methods (Two) - answer1. Local Exhaust Ventilation
2. Dilution Ventilation
The Big Ventilation Equations - answerQ=VxA
Q= air flow (cfm)
V= velocity (fpm)
A= area (ft^2)
Conservation of Airflow (Two laws) - answer1. A1V1=A2V2
2. Q3=Q1+Q2
Local Exhaust System - Basic Components - answer1. Hood (Entry point)
2. Duct - conducts travel
3. Air Cleaner - remove contaminants
4. Fan - Energy source
5. Exhaust Point - Exit
Two types of energy - answer1. Potential Energy - (SP)
2. Kinetic Energy - (VP)
What is Energy (in terms of ventilation)? - answerVentilation in pressure
Velocity Pressure - answer- Always positive
- Force applied by moving air hitting a surface
Static Pressure (ventilation) - answer-relative static pressure - SP in duct in relation to
duct exterior
-force exerted by air molecules striking a surface of a container
-same in all directions
Total Pressure (Equation) and signs pre-post fan. - answerTP = SP + VP
Pre-Fan
TP - neg
SP - neg
VP - pos (always pos)
Post Fan
TP - pos
SP - pos
VP - pos (always pos)
, Ventilation pressure units - answer- Usually inches of H2O
Bernoulli's Equation - answerV = 4005 x Square Root VP
V (fpm)
VP = inches of water
Velocity of non-standard air - answerV = 1096 x square root of VP/ p
V= fpm
VP = inches H2O
p (rho) = lb per ft^3
Energy in ventilation - answer1. Energy to accelerate air in system
2.Energy is used to overcome resistance
Hood Entry Loss - answerDirectly proportional to VP
Energy loss (h) = Fh x VP
Fh = hood entry loss coefficient (look-up)
VP = velocity pressure (inches H2o)
h = hood entry loss
Static Pressure Loss - answerCoefficient of the VP
SPloss = coefficient x VP
Pressure = " h2o
coefficient = lookup
Two hood categories - answer1 External hoods
2. Enclosing hoods
External hoods (includes capture hoods) - answer1. Duct opening
2. Slot opening
3.Compound hood
4. Receiving hoods (canopy, abrasive grinding wheel hood)
Take advantage of contaminant momentum
Canopy hood use - answer-hot process
-minimal cross drafts
Enclosing hoods - answer1. Lab hood
2. Glove Box
3. Paint Booth
Enclosing Hood - Design Criteria - answer1. Cross Drafts
2. Capture velocity (toxicity, phase, contaminant inertia)
Ventilation Methods (Two) - answer1. Local Exhaust Ventilation
2. Dilution Ventilation
The Big Ventilation Equations - answerQ=VxA
Q= air flow (cfm)
V= velocity (fpm)
A= area (ft^2)
Conservation of Airflow (Two laws) - answer1. A1V1=A2V2
2. Q3=Q1+Q2
Local Exhaust System - Basic Components - answer1. Hood (Entry point)
2. Duct - conducts travel
3. Air Cleaner - remove contaminants
4. Fan - Energy source
5. Exhaust Point - Exit
Two types of energy - answer1. Potential Energy - (SP)
2. Kinetic Energy - (VP)
What is Energy (in terms of ventilation)? - answerVentilation in pressure
Velocity Pressure - answer- Always positive
- Force applied by moving air hitting a surface
Static Pressure (ventilation) - answer-relative static pressure - SP in duct in relation to
duct exterior
-force exerted by air molecules striking a surface of a container
-same in all directions
Total Pressure (Equation) and signs pre-post fan. - answerTP = SP + VP
Pre-Fan
TP - neg
SP - neg
VP - pos (always pos)
Post Fan
TP - pos
SP - pos
VP - pos (always pos)
, Ventilation pressure units - answer- Usually inches of H2O
Bernoulli's Equation - answerV = 4005 x Square Root VP
V (fpm)
VP = inches of water
Velocity of non-standard air - answerV = 1096 x square root of VP/ p
V= fpm
VP = inches H2O
p (rho) = lb per ft^3
Energy in ventilation - answer1. Energy to accelerate air in system
2.Energy is used to overcome resistance
Hood Entry Loss - answerDirectly proportional to VP
Energy loss (h) = Fh x VP
Fh = hood entry loss coefficient (look-up)
VP = velocity pressure (inches H2o)
h = hood entry loss
Static Pressure Loss - answerCoefficient of the VP
SPloss = coefficient x VP
Pressure = " h2o
coefficient = lookup
Two hood categories - answer1 External hoods
2. Enclosing hoods
External hoods (includes capture hoods) - answer1. Duct opening
2. Slot opening
3.Compound hood
4. Receiving hoods (canopy, abrasive grinding wheel hood)
Take advantage of contaminant momentum
Canopy hood use - answer-hot process
-minimal cross drafts
Enclosing hoods - answer1. Lab hood
2. Glove Box
3. Paint Booth
Enclosing Hood - Design Criteria - answer1. Cross Drafts
2. Capture velocity (toxicity, phase, contaminant inertia)
