Why Temperature and Humidity Matter When Using NOYAFA JMS12 in Malaysia

Why Measure Temperature and Humidity Together with HCHO and TVOC?

The NOYAFA JMS12 displays four indoor environmental parameters:

Formaldehyde—or HCHO
Total volatile organic compounds—or TVOC
Temperature
Relative humidity

Temperature and humidity do not directly identify chemical pollutants. However, they provide important context when users compare HCHO and TVOC readings between different rooms or at different times.

This is particularly relevant in Malaysia, where indoor environments may alternate between:

Hot and humid conditions
Air-conditioned conditions
Closed rooms
Naturally ventilated rooms
Periods of rain
Hot afternoon temperatures

Without recording these changing conditions, two HCHO or TVOC readings may appear inconsistent even though they were taken in different environments.

How Temperature May Affect Indoor Readings

Certain building materials, furniture and household products may release volatile compounds into the air.

The release rate may change as temperature changes.

Possible indoor sources include:

Composite wood furniture
Built-in cabinets
Laminate flooring
Adhesives
Sealants
Paint
Coatings
Upholstery
Cleaning chemicals

A room that becomes warmer during the afternoon may produce a different reading from the same room measured during a cooler morning.

This does not automatically mean that the detector has developed a fault. The surrounding environment may have changed.

Example: Closed Bedroom During a Hot Afternoon

Consider a newly renovated bedroom containing a built-in wardrobe.

In the morning:

The room is cooler.
The windows have recently been opened.
The air conditioner may have been operating.
The HCHO and TVOC readings are relatively lower.

During the afternoon:

The room remains closed.
Sunlight warms the room.
Indoor temperature rises.
Ventilation is limited.
Volatile compounds may accumulate.

The afternoon reading may therefore be higher.

The JMS12 allows the user to record the temperature together with the HCHO and TVOC readings, making the comparison more meaningful.

How Humidity May Affect the Test Environment

Relative humidity describes the amount of moisture in the air in relation to the maximum amount the air can hold at that temperature.

High indoor humidity may be associated with:

Condensation
Damp surfaces
Uncomfortable room conditions
Mould-related concerns
Reduced drying of renovation materials
Changing sensor response

Humidity should therefore be recorded when comparing measurements taken on different days.

A reading taken during a humid rainy day may not be directly comparable with one taken in a cool, air-conditioned room unless the environmental difference is considered.

Why Malaysian Conditions Require Careful Comparison

Malaysia generally experiences warm and humid conditions. However, indoor environments can vary significantly depending on building design and air-conditioning use.

For example:

A closed condominium bedroom may become hot during the day.
An air-conditioned office may remain cool and relatively dry.
A ground-floor storeroom may be humid.
A west-facing room may become warmer in the afternoon.
A bathroom-adjacent bedroom may experience higher humidity.
A room with open windows may exchange air more quickly.

These differences may influence the way readings develop over time.

For repeatable testing, record temperature and humidity with every HCHO and TVOC result.

What Is Relative Humidity?

Relative humidity is usually displayed as a percentage.

It is affected by both:

The amount of moisture in the air
The air temperature

The same amount of moisture can produce a different relative-humidity percentage when temperature changes.

The humidity reading should therefore be interpreted together with temperature rather than as an isolated number.

Does High Humidity Mean HCHO Is High?

Not necessarily.

High humidity and elevated HCHO are separate observations. A humid room does not automatically contain a high formaldehyde concentration.

However, humidity provides useful supporting information when investigating:

Newly renovated rooms
Enclosed spaces
Damp indoor conditions
Changing readings
Differences between air-conditioned and non-air-conditioned areas

Users should avoid making a direct one-to-one assumption between humidity and HCHO.

Does High Temperature Mean TVOC Is High?

Not always.

A hot room can still show a relatively low TVOC reading if there are few sources of volatile compounds and the area is well ventilated.

Similarly, a cool room may show an elevated TVOC response if:

Cleaning chemicals were recently used
Perfume was sprayed
New furniture is present
Solvent products are stored nearby
Ventilation is poor

Temperature is one factor among several. It should not be used alone to predict TVOC concentration.

Air Conditioning and JMS12 Readings

Switching on an air conditioner may change:

Room temperature
Relative humidity
Air movement
Mixing of indoor air

Depending on the ventilation design, an air conditioner may recirculate indoor air without introducing a significant amount of fresh outdoor air.

A lower room temperature does not automatically mean that pollutants have been removed.

When comparing readings, record whether:

The air conditioner was operating
Doors and windows were closed
Fresh-air ventilation was available
The unit had been operating for a sufficient period

Ventilation vs Air Conditioning

Ventilation and air conditioning are not the same.

Ventilation

Ventilation exchanges indoor air with cleaner outdoor air, depending on outdoor conditions.

This may be achieved by:

Opening windows
Opening doors
Operating an exhaust fan
Using a mechanical fresh-air system

Air conditioning

A typical air-conditioning system may mainly cool and recirculate indoor air.

It can reduce temperature and sometimes humidity, but it may not remove accumulated gaseous pollutants unless fresh-air exchange is included.

This distinction is important when interpreting a lower temperature alongside an unchanged HCHO or TVOC reading.

Recommended JMS12 Test Record

Use a simple table to record every measurement:

Date and time	Location	HCHO	TVOC	Temperature	Humidity	Room condition
Morning	Bedroom centre	Record	Record	Record	Record	Windows open
Afternoon	Bedroom centre	Record	Record	Record	Record	Room closed
Evening	Bedroom centre	Record	Record	Record	Record	After ventilation
Morning	Near wardrobe	Record	Record	Record	Record	Cabinet closed

This record helps users identify whether changing readings are associated with temperature, humidity, ventilation or proximity to a source.

How to Perform a More Consistent Comparison

Use the same detector

Do not compare readings from different instruments without considering their individual sensor tolerances.

Use the same position

Place the JMS12 at approximately the same location and height.

Use a similar stabilisation time

Allow the detector to respond for a consistent period before recording the result.

Avoid interfering vapours

Do not use perfume, sanitiser, air freshener or cleaning spray during the test.

Record room conditions

Note whether windows, doors and air conditioning were operating.

Repeat the measurement

Repeat the test over several days. Trends are generally more useful than one isolated value.

Why Does the JMS12 Reading Change After Moving Outdoors?

Moving the detector from an air-conditioned indoor environment to warm and humid outdoor air exposes it to a rapid environmental change.

The temperature, humidity and gas-sensor readings may require time to stabilise.

Likewise, bringing the unit back into a cold room may temporarily produce changing values.

Do not make an immediate judgment after a large environmental transition.

Allow the detector to adjust before recording the next result.

Can the JMS12 Detect Mould?

The JMS12 measures humidity, but it does not directly identify mould species or measure airborne mould spores.

A high humidity reading may indicate conditions that require further attention, especially when accompanied by:

Visible mould
Condensation
Damp walls
Water leakage
Musty odour

Proper mould assessment may require visual inspection, moisture investigation and specialist testing.

Do not market the JMS12 as a direct mould detector.

Can the JMS12 Measure PM2.5 or CO2?

The standard JMS12 application discussed here focuses on:

HCHO
TVOC
Temperature
Humidity

It should not be treated as a PM2.5 monitor or dedicated CO2 meter unless the supplied specification explicitly states those measurement functions.

For PM2.5 monitoring, select an instrument with an optical particle sensor.

For actual carbon dioxide measurement, select an instrument with a specified CO2 range in ppm and preferably an NDIR sensor.

JMS12 vs JMS11

The JMS11 is suitable for straightforward HCHO and TVOC screening.

The JMS12 is more informative when users want to understand how the room environment changes at the same time.

Feature	JMS11	JMS12
HCHO	Yes	Yes
TVOC	Yes	Yes
Temperature	No	Yes
Relative humidity	No	Yes
Replaceable batteries	Yes	No
Rechargeable operation	No	Yes
Suitable for environmental trend records	Basic	More complete

For repeated property inspections or renovation monitoring, the JMS12 provides a more useful record.

Important Measurement Limitation

The NOYAFA JMS12 is a portable screening instrument.

Its readings should not replace:

Laboratory chemical analysis
Formal indoor air quality assessment
Occupational exposure measurement
Professional mould inspection
Regulatory compliance monitoring
Dedicated PM2.5 or CO2 measurement

Users should consider sensor limitations, possible interfering gases and changing environmental conditions when interpreting the display.

Buy NOYAFA JMS12 in Malaysia

MTM Precision supplies the NOYAFA JMS12 HCHO, TVOC, temperature and humidity tester for homes, offices, renovated properties and general indoor environmental screening.

JMS12 availability
JMS11 versus JMS12 comparison
Updated specifications
Suitable instrument selection
Alternative PM2.5 and NDIR CO2 monitors
Basic operating guidance
Delivery throughout Malaysia
Collection from our Puchong showroom

Contact MTM Precision

MTM Precision Sdn. Bhd. (744811-A)

Telephone: +603-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com / enquiry@mtmpre.com.my
Website: www.mtmpre.com.my

Showroom & Service Centre:
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.